Yet this completely wipes out the savings from not having a car, in most places where not having a car is otherwise feasible, I'd imagine.

But 25 minutes (10 each way and an optimistic 5 to get something, wait in line, check out...) is too long for this use case anyway, in my opinion; it's just barely possible with a car, and I live about 12 minutes walk or 3-4 minutes drive from a store right now.

--and 10 minutes is the outer limit. Good dense places to live have food shops open long hours within 5 minutes walk, because all those people depend on them.