“There is little doubt that the observation that quality may depend on price (productivity on wages; default probability on interest rates) has provided a rich mine for economic theorists: A simple modification of the basic assumptions results in a profound alteration of many of the basic conclusions of the standard paradigm. The Law of Supply and Demand has been repealed. The Law of the Single Price has been repealed. The Fundamental Theorem of Welfare Economics has been shown not to be valid.
More than that, the theories that we describe here provide the basis of progress toward a unification of macroeconomics and microeconomics. They pro vide an explanation of unemployment and credit rationing, derived from basic microeconomic principles. It is a theory in which the extensive idleness that periodically confronts society's resources, human and capital, is seen as but the most obvious example of market failures that prevasively and persistently distort the allocation of resources.”

"The Causes and Consequences of The Dependence of Quality on Price", Journal of Economic Literature, Vol. 25, No. 1 (Mar., 1987)