In Marxian economics, the rate of exploitation is the ratio of the total amount of unpaid labor done (surplus-value) to the total amount of wages paid (the value of labour power).
Thus, the quantity of surplus labour performed by workers in an enterprise might correspond to a value higher or lower than the surplus value actually realised as profit income upon sales of output.
The implication is that if the gross profit volume was related to wage costs to establish the rate of surplus value, this might overstate or understate the real rate of labor-exploitation.
Although this is a subtle point, it has sometimes played an important role in wage bargaining negotiations by trade unions.
For another extreme example, workers might work less hard, knowing that their product will sell like hotcakes in a seller's market at sharply inflated prices, yielding profits disproportionate to labour input.