"Ricardo does understand, and better than Smith, that a good’s price is proportional to its marginal labour cost. But that saves only the face of his verbalistic labour theory of value and not his substantive theory. As soon as changed composition of demand for goods alters endogenously marginal labour embodiments, nothing substantive is left of the labour theory of value."
January 1, 1970
https://en.wikiquote.org/wiki/David_Ricardo