But sometimes in the making of a product certain valuable production goods may be used whose employment does not involve potentiality cost. These are, of course, production goods capable of being used in this one product alone. A production good may be capable of making but one kind of product and yet receive from that product a certain share of value as its productive contribution. A mineral spring may be so situated as to be such a production good. A mine is a perfect example. Here a new question confronts us. Does or does not an entrepreneur’s outlay in the value of such a production good constitute a part of entrepreneur’s cost? This is solely a question as to how we choose to define entrepreneur’s cost. It may be defined either way. But in the event that we define this cost to include outlays for single-use production goods, it will no longer be possible to assert that potentiality cost governs entrepreneur’s cost wholly and in all cases. Let us give an illustration of the question. If the bottled water of a mineral spring can sell for ten cents in a neighboring city, and it costs five cents for the bottle and labor and two cents for transportation, is or is not the three cents per bottle which remains as the rent (“price-determined surplus”) to the spring a part of the entrepreneur’s cost of producing bottled mineral water? If the vender of the water did not own the spring, he would be inclined to reckon the rent paid for it to its owner as a part of his money costs. But economists are agreed that the distinction between costs and surpluses does not hinge on relations of legal ownership. If the producer of the bottled water owned the spring, he would merely pay the rent of it to himself. To the present writer it seems that entrepreneur’s cost may be defined either to be coextensive with potentiality cost, or to exceed this cost by the inclusion of “price-determined” rents,[230] provided a consistent usage be maintained. In the one case, entrepreneur’s cost is determined by potentiality cost; in the other case it is principally determined by potentiality cost.[231]