The notion of prices of production has often been paired to that of reproduction of all the physical quantities of a system. A deeper investigation of Sraffa’s price equations reveals that this association is not well ground, both in the case of subsistence systems as well as in the case of systems with a surplus. The notions of ‘viability’ and that of production prices are thus reappraised in this light, as connected with the possibility that each industry is able to reintegrate the value of the means of production and, if possible, to obtain a positive surplus in value. Viability appears thus a notion that is better understood as a value condition. This specification becomes relevant for an approach where the quantities are taken ‘as given’ while studying the relations concerning value and income distribution. The focus upon non-self-replacing systems, which are systematically in the condition to change their output levels, cannot but open a reflection on the possible specific assumptions that can be made on returns. This aspect is explicitly discussed in relation to the main features of the modern classical approach.