The burden of labor entailed on the man who makes an article stands in no relation to its market value. The product of one hour's labor of an eminent lawyer, an artist, a business manager, etc., may sell for as much as that of a month's work of an engine stoker, a seamstress or a stonebreaker. Here and there are "prisoners of poverty," putting life itself into products of which a wagon load can literally be bought for a prima donna's song. Wherever there is varying personal power, or different position, giving to some the advantage of a monopoly, there is a divergence of cost and value, if by these terms we mean the cost to the producer, and the value in the market. Compare the labor involved in maintaining telephones with the rates demanded for the use of them. Yet of monopolized products as of others our rule holds good; they sell according to the disutility of the terminal social labor expended in order to acquire them. But suppose they are _bought_ with monopolized products, and suppose that a monopoly element enters, at some stage or other, into _every_ product of the market, and in varying degrees in each, either in the form of control of raw material, or special native mental or physical aptitude, or patent right, or any other of the innumerable forms that monopoly takes? Can these monopoly products then call forth a definite amount of social labor? Or can they merely call out a definite amount of value?[85] "_Differences in wealth between different producers cause the cost of products to vary from their value._" (Italics mine.) But surely this is our old circle again. If differences in wealth, which is the embodiment of value, are to modify the working of the "pervasive element" of "personal sacrifice" (p. 263), it is difficult to see how that pervasive element can in any way be an ultimate explanation or measure of value. The rich worker stops producing early, while the sacrifice entailed is still small; but his product sells as well as if it were costly. If we say that the prices of things correspond with the amount and _efficiency_ of the labor that creates them, we say what is equivalent to the above proposition. The efficiency that figures in the case is power and willingness to produce a certain effect. The willingness is as essential as the power.... Moreover, the effect that gauges the efficiency of a worker is the value of what he creates; and this value is measured by the formula that we have attained.