Finally, there are commodities of which, though capable of being increased or diminished to a great and even an unlimited extent, the value never depends upon anything but demand and supply. This is the case, in particular, with the commodity Labor, of the value of which we have treated copiously in the preceding book; and there are many cases besides in which we shall find it necessary to call in this principle to solve difficult questions of exchange value. This will be particularly exemplified when we treat of International Values; that is, of the terms of interchange between things produced in different countries, or, to speak more generally, in distant places. § 5. Commodities which are Susceptible of Indefinite Multiplication without Increase of Cost. Law of their Value Cost of Production. When the production of a commodity is the effect of labor and expenditure, whether the commodity is susceptible of unlimited multiplication or not, there is a minimum value which is the essential condition of its being permanently produced. The value at any particular time is the result of supply and demand, and is always that which is necessary to create a market for the existing supply. But unless that value is sufficient to repay the Cost of Production, and to afford, besides, the ordinary expectation of profit, the commodity will not continue to be produced. Capitalists will not go on permanently producing at a loss. When such profit is evidently not to be had, if people do not actually withdraw their capital, they at least abstain from replacing it when consumed. The cost of production, together with the ordinary profit, may, therefore, be called the _necessary_ price or value of all things made by labor and capital. Nobody willingly produces in the prospect of loss.