Leontief models have reintroduced important elements of the classical approach in modern economic analysis: in particular, the representation of the production process of a society as a circular process and the consequent notion of surplus. The question people must answer is if there exists a price system that allows each industry to recover the expenses of the means of production so that the respective production process can be replicated on an unchanged scale. The prices considered in this example only allow each industry to recover its production expenses. This kind of prices brings people back to the notion of ‘natural’ or ‘normal’ prices, that is, the prices that prevail on average over a sufficiently long period of time. Any innovation in a basic industry will change the rate of profit of the entire system, as well as the price of all commodities, basic and non-basic.