The propensity of men to trade must accordingly have some other reason than enjoyment of trading as such. If trading were a pleasure in itself, hence an end in itself, and not frequently a laborious activity associated with danger and economic sacrifice, there would be no reason why men . . . should not trade back and forth an unlimited number of times. But everywhere in practical life, we can observe that economizing men carefully consider every exchange in advance, and that a limit is finally reached beyond which two individuals will not continue to trade at any given time.
Carl Menger, Principles of Economics (1871; English translation, 1950), Spring 1977, chapter IV, “The Theory of Exchange.”