"Products made in a society of more or less separate private producers, and therefore in the first place private products. These private products, however, become commodities only when they are made, not for consumption by their producers, but for consumption by others, that is, for social consumption; they enter into social consumption through exchange. The private producers are therefore socially interconnected, constitute a society."
"From the moment when society enters into possession of the means of production and uses them in direct association for production, the labour of each individual, however varied its specifically useful character may be, becomes at the start and directly social labour. The quantity of social labour contained in a product need not then be established in a roundabout way; daily experience shows in a direct way how much of it is required on the average. Society can simply calculate how many hours of labour are contained in a steam-engine, a bushel of wheat of the last harvest, or a hundred square yards of cloth of a certain quality. It could therefore never occur to it still to express the quantities of labour put into the products, quantities which it will then know directly and in their absolute amounts, in a third product, in a measure which, besides, is only relative, fluctuating, inadequate, though formerly unavoidable for lack of a better one, rather than express them in their natural, adequate and absolute measure, time. Just as little as it would occur to chemical science still to express atomic weight in a roundabout way, relatively, by means of the hydrogen atom, if it were able to express them absolutely, in their adequate measure, namely in actual weights, in billionths or quadrillionths of a gramme. Hence, on the assumptions we made above, society will not assign values to products. It will not express the simple fact that the hundred square yards of cloth have required for their production, say, a thousand hours of labour in the oblique and meaningless way, stating that they have the value of a thousand hours of labour. It is true that even then it will still be necessary for society to know how much labour each article of consumption requires for its production. It will have to arrange its plan of production in accordance with its means of production, which include, in particular, its labour-powers. The useful effects of the various articles of consumption, compared with one another and with the quantities of labour required for their production, will in the end determine the plan. People will be able to manage everything very simply, without the intervention of much-vaunted “value”. *15
The concept of value is the most general and therefore the most comprehensive expression of the economic conditions of commodity production. Consequently, this concept contains the germ, not only of money, but also of all the more developed forms of the production and exchange of commodities. The fact that value is the expression of the social labour contained in the privately produced products itself creates the possibility of a difference arising between this social labour and the private labour contained in these same products."
Thus, the existence of commodity production and the sale and buying of labour-power contradict Marx's and Engel's ideas on what post-capitalism would look like.