The object of these pages is to revive a critical reflection on the significance of Sraffa's early theoretical work in the five-year period running between 1925 to 1930. After identifying the main interpretive issues, an original historiographic hypothesis is formulated and attention is focused on Sraffa's thought on the shape of cost curves and its consequences on the relationship between price and quantity produced. Sraffa's criticism of Marshall's theory of value was not motivated by reasons of personal convenience, as sometimes has been suggested. He believed that Marshall had severely distorted Ricardo's theory of competitive value, by trying to rebuild it in terms of symmetric relations of demand and supply, in the neoclassical language of market equilibrium. Even Sraffa's early abandonment of his search on imperfect competition - a major element of discontinuity in his theoretical path - may be traced to analytical and methodological reasons. Realising that his idea to afford the study of the behaviour of an imperfectly competitive firm on the assumption that it was faced with a subjective demand curve was in stark contrast both with the basic premises of an objective theory of value and with his critique of the Marshallian method of partial equilibria, he decided to opt for an entirely different analytical approach to the theory of price.