As a child, I once asked my teacher this exact question. In response, I was told this story:

One of the reasons that the rich are rich, is that they manage to spend less money.

Take shoes, for example. A really good pair of leather shoes cost fifty pounds. But an affordable pair of shoes which are fine for a few months and then leak when the cardboard gives out, cost about ten pounds. These are the kind of shoes that poor people can afford to buy.

But the thing is that good shoes last for years and years. A person who can afford fifty pounds has a pair of shoes that will still be keeping their feet dry in ten years' time, while the poor person who can only afford cheap shoes will have spent a hundred pounds on shoes in the same time and will still have wet feet.

This is why - they can’t afford to buy the good quality products that will last, simply because they don’t have the money. This also ends making it difficult to save money in the long term.

People often suggest that poor people/those who are less affluent, bulk buy at places like Costco, forgetting that you have to have a significant amount of money in order to be able to do this. In other words, saving money often costs money to begin with.

Of course, years after this conversation, I finally got around to reading Terry Pratchett’s Men at Arms and instantly recognised this story as being ‘the Captain Samuel Vimes 'Boots' theory of socioeconomic unfairness.’

This doesn’t make it any less true.