As we have seen, the gratifications obtained from the same amount of expenditures for a, b, and c at the margin of indifference of consumption are the same. Likewise the values in use of the amounts of a, b, and c which can be obtained for a given amount of money are the same. But the marginal utility represents capacity to gratify wants, and the value in use represents a power of influencing the choice of the purchaser. Therefore, they are different kinds of things. But the values in use of these various goods vary as their marginal utilities vary, relatively to the values in use and the marginal utilities of other goods.

In this explanation of value in use we have introduced the idea of the price of goods in the market. This idea will be discussed later in connection with the discussion of value in exchange. But it was necessary to introduce it at this point because as a matter of fact the value in use of goods to us is influenced by their market price. If goods could be had without cost, marginal utilities and value in use would both sink to zero. If we were considering the case of value in use in the stage of independent household economy where there was no market and no exchange we should need to compare not the amount of various kinds of goods which could be purchased for a given amount of money as we have done here, but the amount of the various kinds of goods which could be secured by a given expenditure of physical and mental effort.

The term value in use was used by Adam Smith and certain other economists following him to mean utility or usefulness. In this sense of the term the value in use of several units of a commodity is dependent upon the total utility of those units and not upon their marginal utility. But the meaning of value in use given above is better present-day usage. We can get an indication of the value in use of a given supply of a commodity by multiplying the marginal utility by the number of units in the supply.