" In fact, this can happen only when the conditions for commodity
production and exchange are equal for all members of society; that is to
say, when they are all independent owners of their means of production
who use these means to fabricate the product and exchange it on the
market. This is the most elementary relationship, and constitutes the
starting point for a theoretical analysis. Only on this basis can later
modifications be understood; but they must always satisfy the condition
that, whatever the nature of an individual exchange may be, the sum of
exchange acts must clear the market of the total product. Any
modification can be induced only by a change in the position of the
members of society within production. In fact, the modification must
take place in this manner because production and the producers can only
be integrated as a social unit through the operation of the exchange
process. Thus the expropriation of one section of society and the
monopolization of the means of production by another modify the exchange
process, because only there can the fact of social inequality appear.
However, since the exchange relationship is one of equality, social
inequality must assume the form of a parity of prices of production
rather than an equality of value. In other words, the inequality in the
expenditure of labour (which is a matter of indifference to capitalists
since it is the labour expenditure of others) is concealed behind an
equalization of the rate of profit. This kind of equality simply
underlines the fact that capital is the decisive factor in a capitalist
society. The individual act of exchange no longer has to satisfy the
requirement that units of labour in exchange shall be equal, and instead
the principle now prevails that equal profits shall accrue to equal
capitals. The equalization of labour is replaced by the equalization of
profit, and products are sold not at their values, but at their prices
of production. "

― , Finance Capital: A study in the latest phase of capitalist development