_How Different Classes of Purchasers cooeperate in this Price Making._--The rule of one price for one article of course holds, and the man who would have a clear and decisive motive for buying the A for more than ten dollars, if he had to do so, gets the benefit of two facts: first, that it costs only that amount in the producing, and secondly, that competition makes the supply of it so large that it is brought within the reach of those persons who value it at only ten dollars. It takes two different classes of purchasers to fix the price of this package of two articles, and their ratings fix it at twenty dollars. Exactly the same influences regulate the price of the bundle which includes A, B, and C. Men who buy C can afford to have a luxury, and therefore, if they had had to do so, would have given more than they do give for the articles of necessity and comfort. If the price of A and B were higher than it is, they would still buy these two things, but they would not raise their bids for C, since for this they are marginal purchasers. This commodity is therefore sold at the price that will just induce this class of persons to add it to their list of consumers' goods. There is a further class in whose list of purchases D is marginal, while A, B, and C yield a consumers' surplus in the form of an uncompensated personal benefit. _Different Utilities in an Article appraised as are Different Goods in a Package._--It is an actual fact that most commodities are like these packages of unlike articles. They are bundles of unlike utilities, and the market actually finds a way to analyze composite things and put a separate price on each utility. It may seem very theoretical to say that a concrete thing, like a watch, a coat, a dining table, or a roast fowl, is made up of such abstract things as utilities and that each of these has its separate price; yet such is actually the fact, and if goods were not valued in the market in this way, the prices of all articles of comfort and luxury would be very much higher than they are.