John Stuart Mill,
Principles of Political Economy
(1871)
“ The buyers must be supposed as studious to buy cheap, as the sellers to sell dear. The values and prices, therefore, to which our conclusions apply, are mercantile values and prices; such prices as are quoted in price-currents; prices in the wholesale markets, in which buying as well as selling is a matter of business; in which the buyers take pains to know, and generally do know, the lowest price at which an article of a given quality can be obtained; and in which, therefore, the axiom is true, that there cannot be for the same article, of the same quality, two prices in the same market. ”
