One of the contentions I ocassionaly hear is that the market price is generally the just price. I’m not sure what the principles or arguments that establish this but it seems reasonable. However there are instances when the market price taken as the common estimation of the market is unjust.
Since the market price is the common estimation of the market, this estimation may be wrong. If for example, there is a general error in economic thinking the value of something may be incorrect.
In the case of usury, nothing is seen to have some value. Men are charged for non-being and this finds a place on balance sheets becoming part of the general valuation of a firm. Since nothing can have no value, all such valuations would be wrong and the market price would be systemically different from the just price. Hence the market price would be unjust.
We may then suggest that the market price under certain conditions is generally the just price, as presently in the US the market price is not. The project then would be to determine the conditions that establish at least a general congruity.