> People do this constantly, some to a comical degree, going so far as to make two loops on their shopping trip to return groceries they found cheaper at the next store.

To go less far, it is pretty common for normies to have at least two supermarkets in their shopping list: one with lower prices and one with higher prices, but fancier goods.

I have never heard of someone returning groceries (unless it turned out to be moldy or something). Definitely not because they were cheaper elsewhere. Surely there would be food safety issues with accepting such returns.

You may be assuming a car-centric approach to shopping, where the distance between stores is large. In cities where shops are mixed into residential areas, people often walk because stores are usually within about 10 minutes, and there are multiple options with different selections and prices.

That makes it easy to rotate: stop by one store one day, another the next, often on the way home from work since you’re taking the subway or bus anyway. For example, I buy most of my groceries at one store, and then pick up certain items in bulk at other stores every 1-3 months when they carry the brand I want at a good price (unless my usual store has a sale). Most people I know do something similar, especially as groceries have gotten more expensive, particularly since COVID.