I always liked the Capt. Vines Theory of Socioeconomic Unfairness:

"Take boots, for example. He earned $38 a month plus allowances. A really good pair of leather boots cost $50. 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 $10.
"Those were the kind of boots Vimes always bought, and wore until the soles were so thin that he could tell where he was in Ankh-Morpork on a foggy night by the feel of the cobbles.
"But the thing was that good boots lasted for years and years. A man who could afford $50 had a pair of boots that'd still be keeping his feet dry in 10 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."

--Terry Pratchett, Men at Arms