Corrupt

The central idea of Michael Sandel's book is simple: If we treat everything as a commodity and put up a price for sale, we will downgrade many invaluable human virtues - their true value would be corrupted, and their place in our behavioral norm being crowded out.

(For example, if we accept buying blood from "professional" donors, there would be fewer voluntary ones.)

When you come to think of it, the basic idea is a variant or extrapolation of Maslow's hierarchy. In short, money is, in reality, the symbolic representation of our basic human need - food, clothes, shelter, and so forth.

However, when these fundamental aspects are satisfied, we long for higher levels of fulfillment - friendship, love, sense of belonging, being respected, and self accomplishment. None of these could be bought by money. What Sandel tries to show us is by treating these higher needs as commodities and calculating their monetary cost, we actually downgrade their meaning and corrupt their value.