$3.50 for a café au lait: Affordable. $8 for a tuna melt: Too much. 99 cents for an app: Unnecessary. $600 for an iPad: Essential! How exactly do we decide what’s a necessity and what’s a luxury? Real Simple investigates.

By Amanda Fortini
Updated April 16, 2013
Michael Rosenfeld/Getty Images

Last January, at a department-store outlet, I purchased a pastel-flecked sweater, gray corduroy jeans, and a pair of powder blue silk trousers—all designer, and all for around $300. The pants especially felt like a coup: Originally priced at $1,200, they were on sale for $92. What a bargain, I thought, as I handed over my credit card. Although none of my purchases were necessities (powder blue silk trousers?) and I was still feeling the pinch of the previous month’s holiday gift-buying bonanza, I went into the fuzzy, soft-focus state that frequently overtakes me when I’m shopping. Suddenly, I lack the ability to reason, to think of anything—the health-insurance premium I have yet to pay that month, the article for which I’ve yet to be paid—except the purchase at hand. I might have remained in this gauzy mode had the saleswoman not intruded: “You’re quite the shopper,” she said, glancing down at her computer screen. “In the past seven years, you’ve spent enough to buy a small car.”

Setting aside the meddlesome strangeness of her comment, I was mortified. I began to contemplate, for the first time ever, how difficult it is for me to wrap my mind around what I can and can’t afford. I am someone who digs out the dregs at the bottom of a tube of lipstick before buying a new one and who refuses to order soy milk steamed from the coffee shop because it costs 15 cents more. Yet I’d frittered away this much money on clothing? I thought about all the other ways I could have used that money: I could have opened a retirement fund, made a down payment on a small house, or, yes, bought a car. I wondered, as I left the store, why I always feel that I can afford to buy new clothes, but I seem to believe that these other expenditures are out of my reach.

The question of what is and isn’t affordable would appear to be a fairly straightforward one. After all, if we have the money to pay for something—either outright at the time of purchase or when the credit-card bill comes due—then we can afford it, right?

It turns out that reality is more complicated. “People have very elastic ideas about what they can afford and what they can’t,” says psychologist Michael Cunningham, a professor at the University of Louisville, in Kentucky, who studies monetary decisions. “Sometimes people think, If I can find a way to pay for it and take it home, that means I can afford it, as opposed to considering whether it fits into a strict budget.” After all, when we’re in line, about to spring for a stash of fancy new cosmetics, say, or a high-end bottle of wine, how many of us are mentally reviewing the finer details of our budget? In those moments, our notion of what we can afford is influenced by a host of other factors. According to the experts, here are five key influences.

1. A Culture of Consumption

My grandmother, who is a child of the Great Depression, is perplexed by my need for so many clothes. “I always had three bras, three skirts, and three sweaters,” she is fond of saying. “One in the drawer, one in the wash, and one on.” Her frugal ethos—buy only what you need; live within your means—was more prevalent at midcentury.

Back in 1959, the personal-savings rate (the percentage of disposable income set aside for retirement or other savings) was 7.5 percent; even in 1973, it was 10.5 percent. But as early as World War II, our spending habits had already begun to shift. Returning veterans educated under the G.I. Bill found well-paying work; they bought homes, which had to be filled with furniture and appliances, and so they shopped.

Consumer goods soon became the mainstay of the U.S. economy. Between 1945 and 1949, Americans bought 20 million refrigerators, 21.4 million cars, 5.5 million stoves, and 11.6 million televisions, according to historian Elaine Tyler May. Not only was buying promoted as a patriotic duty, but the war had left Americans “wealthy and acquisitive, resulting in a shift from saving (or Depression-era deprivation) to instant gratification that has characterized the average American’s personal economy ever since,” writes Colin Harrison in American Culture in the 1990s ($29.50, amazon.com).

By the early 1970s, rising wages and decreasing family size were among several factors that induced consumers to spend proportionally less of their household budget on necessities, like utilities and food, and more on discretionary expenditures, such as entertainment and recreation. The share of women in the workforce, which had risen to 37 percent, further increased total household income.

It was in the late 1970s and 1980s that consumer spending began to truly surge, as lower- and middle-income Americans gained greater access to consumer credit and home equity; the savings rate began an accompanying decline. By the mid- 2000s, the savings rate had dipped as low as 1.5 percent, and low-interest adjustable-rate mortgages persuaded people to buy McMansions they couldn’t afford.

Fueled by consumer credit, clever advertising, and enticing marketing campaigns, mass consumption has become the hallmark of our modern society. Everywhere we go, everywhere we look—on television, on billboards, during movie previews, as soon as we log on to the Internet—we are urged to buy. “The decisions we make are largely a reflection of the environment we’re in,” says Dan Ariely, a professor of behavioral economics at Duke University, in Durham, North Carolina, and the author of Predictably Irrational: The Hidden Forces That Shape Our Decisions ($16, amazon.com). “And almost everything in our environment tells us to spend money now, spend attention now, spend effort now.” Cunningham agrees: “Today’s cultural dynamic doesn’t emphasize thriftiness but instead encourages immediate gratification. And there are a lot of cultural forces encouraging people in that direction.” He adds, “We have created a consumer culture that is highly effective at getting people to consume.” Even when we can’t afford to.

2. Emotional Buying

Chances are, you probably can’t count the number of times that you’ve bought something because you thought to yourself, I’ve had a bad day at work, so I’m going to treat myself, or, I’m exhausted, so I’ll buy this because it’s convenient. (The latter often translates into excessive dinners out.) “A lot of our financial decisions are made with our emotional brain,” says Brad Klontz, Psy.D., a Hawaii-based financial psychologist and the author of Mind Over Money: Overcoming the Money Disorders That Threaten Our Financial Health ($25, amazon.com). “When we become emotionally charged, we become rationally challenged. If we’re feeling lonely or sad or anxious, for example, that limits the capacity of our prefrontal cortex to regulate our behavior and makes us more vulnerable to buying.”

When we buy for emotional reasons, the assumption is usually that a particular purchase—whether it’s a brand-new flatscreen television or the latest It Bag—is going to make us happy, or at least happier than we currently are. However, research has shown that while there is an immediate gain in contentment from purchasing something, “you adapt to the pleasure that you get, and then you take the item for granted,” says Miriam Tatzel, Ph.D., a professor of human development at the State University of New York Empire State College, in Nanuet, and the editor of the forthcoming volume Well-Being in the Material World. This tendency, known as “hedonic adaptation,” can lead to a phenomenon called the “hedonic treadmill,” in which we are driven “to acquire ever more new and thrilling things,” says Sonja Lyubomirsky, a professor of psychology at the University of California at Riverside, who studies human happiness. “You’re always wanting more or better,” adds Tatzel, “or looking to upgrade what you already have.”

3. Keeping Up with the Joneses

Many of us tend to prioritize purchases that we believe will raise our esteem in the eyes of others. We are convinced that a pair of Christian Louboutin shoes, with their signature fire-engine red bottoms, or a house in the right neighborhood will signal our success. “People who are really focused on external validation will tend to value possessions that have more public display,” says Tatzel. Sometimes people will also forgo other, arguably more important, expenditures, like upgrading the furnace, in order to make these flashy purchases.

Experts say that many of us feel a strong compulsion to buy what those in our workplace or social milieu possess; we believe we need, should have, and can afford whatever they have. “It’s part of the herding instinct, and it is meant to increase our survival,” says Klontz. “Which worked great back when you needed warmer clothes to live through the winter or better access to the food supply, but which works terribly in modern culture, where we’re inundated with media.”

Our constant exposure to images of the luxurious homes on The Real Housewives or the extravagant fashions of tabloid celebrities has caused that instinct to backfire. “Years ago, we used to compare ourselves horizontally, to the Joneses next door,” says Manisha Thakor, the founder and CEO of Santa Fe–based MoneyZen Wealth Management. “And typically the Joneses next door had incomes similar to ours. When you were looking at what your neighbors were doing, it really was a pretty accurate reflection of what you could be doing.” Now “we compare ourselves vertically to people in wildly different income spectrums,” Thakor explains. We try to “keep up not just with the Joneses but with the Zeta-Joneses,” she says. “We look to the rich and famous, and we try to emulate their lifestyles.”

4. Easy Access to Credit

The mere fact that we only have to swipe our plastic (or enter its digits online) to make a purchase can cause many of us to feel that we can afford just about anything we desire. “Is the credit card not maxed out? That means you can pay for it. So that means it’s affordable!” says Cunningham, articulating a common consumer mind-set. Since physical money never changes hands, we’re apt to forget that actual dollars and cents are at stake; the “pain of paying” is eliminated, to use a term from behavioral economics. This may explain why we’re often irked by the price of small, quotidian items (remember that soy milk?). We tend to pay for these with cash and thus feel the transaction viscerally—whereas large purchases, such as costly patio furniture, might not bother us as much because we usually use a credit card, and the money exchanged remains invisible.

Credit cards also expose a common human weakness: People find it challenging to project into the future and imagine the opportunity cost associated with a purchase—that is, the trade-off, since money used to do or buy one thing can’t be used to do or buy something else. “Decisions about money are all about now versus later,” says Ariely. “If you buy a cup of coffee, you buy shoes, you buy a car, something will have to give, but the reality is that it’s really hard to understand what will give.” Will you not have money for a new dishwasher? Will you have to brown-bag it for a month? Credit cards obviously eliminate the need to make a choice.

5. Getting a “Good Deal”

Finally, we tend to think that an item is affordable when we’re convinced that we’re getting a good deal. We tell ourselves that we won’t find this bargain elsewhere, that we absolutely need five pairs of the same discounted leggings, or that we’re preventing greater monetary losses by purchasing this, the on-sale cookware, rather than the full-price Le Creuset. We forget that money always has an opportunity cost and that even if we’re getting a bargain, we won’t have that money to use in another way.

Plus, here’s the catch: Because we’ve ostensibly saved money, we’re then more likely to overspend. “You save your money in one area, and you may end up spending it in another,” says Christopher Daggett, a senior associate at the New York City– based behavioral consulting firm ideas42. Daggett cites as an example a study in which users of Airbnb, the peer-to-peer lodging company, saved money on lodging in San Francisco but then ended up staying longer and spending more on their trips overall than did hotel guests. Aren’t we all guilty of this? A friend pays for dinner, so you take a cab home instead of public transportation. You don’t eat out for a week, so you feel you have the leeway to splurge on an expensive haircut. Whatever the item or service in question, you think you can afford it because you’ve gotten a compensatory deal in another area. “People think of all the money they’re saving, not the money they’re spending,” says New York City–based psychologist April Lane Benson, who works with shopaholics and is the author of To Buy or Not to Buy: Why We Overshop and How to Stop ($19, amazon.com).

So were my $92 powder blue silk trousers affordable? On the one hand, I’m guilty of several of the aforementioned rationales for buying. I purchased them with fantasies of impressing my chic-est friend, told myself that I’d landed a bargain, and paid for them with my credit card. Did I need them? Admittedly, no.

Even so, they were a beautiful, high-quality item being sold at a price that fit my budget. And finally there’s this: According to research, that human tendency to adapt to any purchase, big or small, means that buying smaller, lovely things more frequently (rather than making a few large purchases) tends to maximize happiness. That I can afford.