It’s long been believed that one reason stores like Costco are so popular is that they allow people to buy, for instance, a whole winter’s supply of canned soup at a per-unit price that’s far below that of soup at the grocery store. But the study points to another reason bundled packages sell so well. If a store sells individual cans of soup, people will be more likely to buy from a mix of brands, and will probably buy only a few cans. Instead, a store can, like Costco, sell a bunch of cans of a single brand together. In this setup, shoppers’ preference for a large, unvaried bundle is, according to this study, strong enough to convince them to buy more cans than they would have if those same cans were sold individually.

In other words, people might be more comfortable with buying a forkliftful of paper towels simply because they aren’t purchasing it one roll at a time, and they’re more likely to be okay purchasing a quantity they otherwise would’ve rated too big.