Section C. Prices In General. The price of a commodity is its value in exchange expressed in the quantum of some other definite commodity, against which it is exchanged or to be exchanged. Hence, it is possible for any commodity to have as many different prices as there are other kinds of commodities with which it may be compared.(597) But whenever price is spoken of, we think only of a comparison of the commodity whose value is to be estimated, with the commodity which, at that time and place, is most current and has the greatest capacity for circulation. (Money.)(598) When two commodities have changed their price-relation to each other, it is not possible, from the simple fact of such change of relation, to determine on which side the change has taken place. If we find that a commodity A stands to all other commodities, C, D, E etc., in the same relation as to price as before, while commodity B, compared with the same, has changed its place in the scale of prices, we may infer that B, and not A, has left its former position.(599) The words costly and dear, as contradistinguished from common and cheap, both indicate a high price. We, however, call a commodity costly whose price, compared with that of other similar commodities, is high. On the other hand, we call a commodity dear when we compare it with itself, and with its own average price in other places and at other times.(600) In individual cases, the price of a commodity is determined most usually, and at the same time most superficially, by custom; people ask and pay for a commodity what others have asked and paid for it. If we go deeper and inquire what originated this customary price and may continually change it, we come to the struggle of interests between buyers and sellers. And if science would analyze the ultimate elements of the incentives to this struggle and the forces engaged in it, it is necessary that it should keep in view the entire economy of the nation, and even all national life. Section CI. Effect Of The Struggle Of Opposing Interests On Price.