al._--A consumer always
gets a net surplus of benefit from the early increments of the goods
he consumes. If the last barrel of apples is worth two dollars,--or,
what is the same thing, if the last barrel has in it an amount of
utility equal to the final utility of other things that two dollars
will buy,--the first barrel has a larger utility; and yet it costs no
more than the last one. The sellers of apples, if they expect to
dispose of all that they have, must at the outset fix the price at
such a point that the very last increment of the supply will
successfully compete with other articles for the favor of purchasers.
Competition forces them to sell the whole amount so cheaply that the
least important part of it may be as important to the purchaser of
that part as the corresponding and least important part of the supply
of other things. Nothing but a monopoly of the entire available stock
would enable them to carry out the auctioning plan and offer the stock
piecemeal, so as to get a higher price for the parts offered early.
Even then buyers who should perceive the fact that a large part of the
stock remained in reserve and that it must ultimately be sold would be
able, by delaying their purchases, to get the benefit of a later and
lower rate, so that the monopoly itself would be only partially
successful in its policy. In the absence of a monopoly venders are
compelled to sell all articles of one kind and quality at one price.
The man who should fix a higher price on his portion of the supply
would be passed by in favor of other sellers who were disposing of
their final increments, and his business would quietly drift away from
him. _There cannot be two prices for one commodity in the same market_
at the same time. This fact is fundamental. Even the monopoly is able
to get different prices for different parts of its output only by
offering them at different times; and competing producers cannot do
this. They are forced to keep the price of all they offer at a level
that expresses its final utility.

_The Law of Value affected by the Difficulty of using Two Similar
Goods at Once._--There are two imperfections in the common statement
of this law of final utility which need to be removed in order that
the theory of value, which is based on the law, may be true and
useful. The first lies in the assumption that people buy completed
articles, such as coats, tables, vehicles, watches, etc., in regular
series of units, add