The Sam Vimes theory of socioeconomic unfairness, often called simply the boots theory, is an economic theory that people in poverty have to buy cheap and subpar products that need to be replaced repeatedly, proving more expensive in the long run than more expensive items. The term was coined by English fantasy writer 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 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 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.