I think you are asking, essentially, why there are no retail non-profits. Operate them like a charity for the common good, etc, but all you do is sell stuff. No fancy human rights work or animal rescue. Just sell stuff. Cheap. As a non-profit.

Here’s the best possible answer to this: good idea - go do it.

I think what you will find is that you can’t get any kind of investment to help you, not even a small business loan. So it’ll be hard for you to compete at all. And in the beginning you’ll be so small that you probably won’t be able to sell for less than the big stores. They buy at special lower prices because they are so big. You don’t get that. And even if you frame the whole thing as a charitable enterprise to help the poor, who will your donors be? Why would anyone give their money to this cause over something that helps the most vulnerable directly?