UNDER SOCIALISM, BUYING EVEN ONE ROLL IS A PRIVILEGE: The Privilege of Buying 36 Rolls of Toilet Paper at Once.

“One of the great ironies in modern America,” writes Mehrsa Baradaran in her 2015 book How the Other Half Banks, “is that the less money you have, the more you pay to use it.” Baradaran, an associate professor at the University of Georgia’s law school, was referring to the outrageously high fees that low-income workers must pay to “fringe” banks just to access and manage the money they’ve earned.

Her point—that when people don’t have much, a single dollar in some ways doesn’t go as far as it otherwise would—extends to several other parts of Americans’ financial lives, including how they shop.

In a recent working paper, the University of Michigan’s A. Yesim Orhun and Mike Palazzolo, point to how two of American shoppers’ (and marketers’) favorite money-saving strategies, the limited-time offer and buying in bulk, come with savings that are more accessible to some consumers than others. Choosing to buy things when they’re on sale or packaged in huge quantities is something lots of shoppers may take for granted as a matter of preference, but for many, these purchases—and the savings that come with them—are out of reach. . . .

These differences produce a striking pattern: Orhun and Palazzolo calculate that because low-income shoppers don’t take full advantage of sales and buying in bulk, they end up paying about 6 percent more per sheet of toilet paper than high-income households. At the same time, lower-income households seem to be compensating for this premium by buying cheaper brands—a trend working in the other direction, saving them about 9 percent per sheet, compared to high-income households. “Therefore,” Orhun and Palazzolo write, “about two-thirds of the savings low income households accrue through brand choice is forfeited by their relative inability to utilize intertemporal money-saving strategies.” (Whether products with fancier brand names are truly better, and whether it’s a loss to miss out on them, is another matter.) . . .

On top of that, Orhun and Palazzolo’s data suggests that poorer and richer consumers aren’t just buying products in different quantities—they’re sometimes doing so at different stores entirely. At corner stores, the price per sheet of toilet paper (or paper towel, or tissue, and so on) is much higher than at warehouse stores such as Costco and Sam’s Club—stores where the average customer tends to be somewhat well-off.

You can offset a lot of this via Dave Ramsey style money management, better meal planning, and strategic shopping. If you’re too poor for those, your poverty probably stems from deeper problems like drugs or mental illness. And, of course, one reason people are poor is that they have trouble making and sticking to plans.