Because the money he spends raises the price of goods etc. Therefore your 20,000 becomes less money. This is easy too see in expensive cities. The same middle-c

Because the money he spends raises the price of goods etc. Therefore your 20,000 becomes less money. This is easy too see in expensive cities. The same middle-class person would have to demand more money to live at the same standards as he/she would have elsewhere, simply because richness have driven up the prices.