§6. _The Diminishing Utility of Money_. But one important point must be emphasized in this chapter. The utility which a business man derives from the things which he buys for business purposes is the extra receipts which he obtains thereby. Derived utility, in other words, is expressed in terms of money, and the idea of its relation to price presents no difficulty. But the utility of things which are bought for personal consumption means the _satisfaction_ which they yield, and this is clearly not a thing which is commensurable with money. When, therefore, it is said that the prices measure their respective marginal utilities, what exactly is meant? What was it that the argument of §3 went to show? That the utility of the marginal pound of sugar would seem to the housewife just worth the price that she must pay for it; in other words, that it would be roughly equal to the utility she could obtain by spending the money in other ways. The respective marginal utilities which _she_ obtains from the different things she buys will thus be proportionate to their prices. But if she were to receive a legacy which gave her a much larger income to spend, she might buy larger quantities of practically every commodity; and, though she would obtain a greater total utility thereby, the marginal utility she would obtain in each direction would be smaller, in accordance with the law of diminishing utility. The prices might not have changed; the respective marginal utilities to her of the different things would again be proportionate to their prices, but they would constitute a smaller satisfaction than before.