in buying it he realizes a consumers' surplus; but for the article B,
which is tied to it, he may pay all that it is worth to him. For that
he is a marginal purchaser, and as such he gets no consumers' surplus
out of it. What he pays for B will just suffice to buy something else
which is equally important to him. The price of this bundle of two
articles is ultimately determined by the cost of the two components,
which is twenty dollars, and enough of each component is made and
offered in the market to supply the wants of a class of persons who
will barely decide to take it at the cost rate. The class that
hesitates at taking A will not consider B, but the class that
hesitates at taking B gets a clear benefit from buying A at the price
that expresses the utility of A to a poorer class of persons.

_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 e