"Behind the prejudice, though hardly ever explicitly expressed, lies a real paradox, namely, the syllogism that:

(a) a trade should be fair;
(b) if a trade is fair, both sides remain with the same value;

whence it follows that

(c) if a person can increase his capital by trade, he is cheating someone."

No šīs jaukās D. Schaps grāmatas:
http://www.amazon.com/Invention-Coinage-Monetization-Ancient-Greece/dp/047211333X