Leis da acção humana

"The value of what you have got is not affected by the value of what you have relinquished or forgone in order to get it. But the measure of the advantages you are willing to forgo in order to get a thing is determined by the value that you expect it to have when you have got it.

(Wicksteed, Com­mon Sense of Political Economy, I, 93 and 89) - via Man, Economy, and State, Rothbard