Similar to the boots theory from the late Sir Terry Pratchett.

The reason that the rich were so rich, Vimes reasoned, was because they managed to spend less money. Take boots, for example. … 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 a 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.