Wages don't have to be equal to marginal revenue products. And since paying people their marginal revenue products is often very unfair -- Michael Jordan gets $20 million a year and a nursery school teacher gets $20 a year -- an equitable economy requires us NOT to pay according to MRP. But, for a market system to be efficient goods, and inputs for making goods, need to be priced according to their opportunity costs. The opportunity costs of different kinds of labor IS precisely their different MRPs. Otherwise users will over and under use different kinds of scarce labor resources that they have to pay less or more respectively than their MRPs. The answer, of course is to charge users of labor according to their opportunity costs -- that is their different MRPs -- but to pay people according to effort, or personal sacrifice since that is what is fair and equitable. It is possible to do this in a planned economy -- and we do it in participatory planning -- but I know of no competent economists who has argued that it is possible to do this in a market economy.
