> the ability to both afford next week’s food this week

At minimum that's everyone on a normal paycheck, paid every two weeks. There are situations where someone couldn't get together a few days' pay at once, but that's a tiny fraction of situations.

And the means to store most food is a two foot square of space in a room somewhere. And then most of the rest fits in the empty fridge space you already have.

And there are deals there that can be useful for your wallet right away. This isn't something where you have to put up a ton of money for months before you benefit.

The biggest issue is probably that costco isn't easy to get to.