They patiently explained to idiot me that the reason they ate so poorly was because finding $100 was effectively impossible.
With community support you can pool your money, then split the goods and the savings.
But you have to be able to implicitly trust your community.
Do your friends have other friends in similar situations? Do they trust them enough to make pooled purchases?
(Also, you start with pooled purchases simply to help your community. Eventually that transitions into making a bit extra, and before you know it you opened a store. If you are a good person, then you continue to quietly help people in your community with discounts or credit.)
Maybe not everyone can buy bulk but you can buy expired goods, grade b veg, etc.
It may not be logical, but I accept it as one of the quirks of human behavior. Similar to how pointing out the economic nature of some relationships and interactions is often considered creepy and anti-social (for example, pointing out how certain commonly assumed altruistic behaviors are not altruistic).
But that just proves the broader point: it's not the mere $100 that's holding them up; it rarely is. Rather, it's the practice of not thinking long term, and not accumulating savings even when you have clear opportunities.
Regardless of the terms of repayment (even if there are no terms), it adds stress to future encounters, and they may outright refuse it out of principle anyway.
Unrelated, but I seriously doubt you could eat for three months for $100 at Costco unless you subsist on bulk oatmeal and other dry food.
That's supposedly what they're doing now. You could just buy the rice/beans in much larger bulk than normal grocery stores so the money lasts longer.
'Normal' meals with fresh veggies and some meat/etc? You're right.