Comment by gruez

>We (the 99.9%) are not poor enough. We can still afford it "in some sense" and to some degree". The poorest, say, 30% shield the rest of a society from paying too much.

It's not necessarily "the poorest [...] 30%". It's the marginal consumers who's willing to comparison shop and put in the legwork. They keep prices down for everyone else, by threatening to switch to the other store if one store decides to get too greedy. True, being poor might be correlated with putting the legwork into saving money, but wealth isn't the definite factor.

>p.s. If you know this idea has some academic name, please lemme know!

sounds like https://en.wikipedia.org/wiki/Economic_surplus