Also, and this is true for many things, the poor are less capable of spending more money now to save money over the long term. E.g., if a pair of boots that will last 3 years is $150 and a pair of boots that will last 6 months is $30, the $150 pair of boots is a better deal because you'd have to buy $180 dollars worth of cheap boots to last 3 years. But if you only have $50 available to spend and you need new boots now, you have to choose the cheap boots.

So, forget buying everything in bulk, or buying a membership to a warehouse club.