Terry Pratchett had a really perfect explanation for one of the many reasons why it’s more expensive to be poor than to be rich:
“Take boots, for example. He earned thirty-eight dollars a month plus allowances. A really good pair of leather boots cost fifty dollars. But an affordable pair of boots, which were sort of ok for a season or two and then leaked like hell when the cardboard gave out, cost about ten dollars.
But the thing was that good boots lasted for years and years. A man who could afford fifty dollars had a pair of boots that’d still be keeping his feet dry in ten years’ time, while the poor man who could only afford cheap boots would have spent a hundred dollars on boots in the same time and would still have wet feet.
This was the Captain Samuel Vimes ‘Boots’ theory of socioeconomic unfairness.”
-Terry Pratchett, Men at Arms
By this model, one reason the rich are so rich is because they manage to spend less money… and not just on boots.