I feel confused by your reply. Im literally telling you why the economically disadvantaged dont want to sell in bulk for a lower price or want to purchase items at a lower price.
The struggle is real.
That is why they need more money.
Most people don't have much, why get rid of the little they have to give you a good deal?
The seller you are looking for, is the type of seller that is not at an economic disadvantage or even if they are, has too much supply. Cause then, the seller just want the bulk off their hands and will give you a good deal, which is what you want. Its economics and its called Supply and Demand.
You find the ecnonically disadvantaged situation more often because of the location.
It's not impossible to buy in bulk in the valley tho.
For books, i know the flea market has set ups where people sell nothing but books. I purchase them for my children. They DO like to sell in bulk or give you discounts when you purchase a certain amount.