Böhm-Bawerk’s theory of price is the only attempt that has been made to complete the utility theory in this direction, which is at once well known and authoritative.[219] Though the fundamental lines of this explanation are correct, it is in externals at least defective in two noteworthy respects. In the first place, one of its principal assumptions is untrue to the typical conditions of exchange under the division of labor. This assumption consists in supposing that sellers’ subjective valuations are effective factors in determining price in the market of an organic society. In Böhm-Bawerk’s theory, the reader will recall, the miniature but supposedly typical market is assumed to consist of a number of sellers owning horses and a number of buyers desiring them. The first step in the argument is to assign a money expression to the esteem or “subjective” value of a horse to each buyer and each seller. Then if these money expressions, or “price equivalents,” are higher for some one buyer than for some one seller an exchange of money for a horse is possible between the two. If buyer B values a horse at $45 and seller S at $40, B can afford to part with, and S can afford to take for a horse any sum of money over $40 and under $45. By considering all the price equivalents of sellers on one side and of buyers on the other side, Böhm-Bawerk shows us that for every given combination of such figures in a market there is a certain definite number of sales possible, and these sales must take place at a price fixed between the price equivalents of the last buyer and the last seller. In other words, the market price will be fixed between the money valuations set upon a horse by the “marginal pair.” The region so delimited by the marginal pairs becomes narrower as the number of buyers and sellers entering the market increases. Thus, in a large market the price is virtually determined to a point. The difficulty with this theory is that under the division of labor, sellers make products for the market, in view of the market price, and make them in numbers and keep them in stocks far in excess of their own needs. Under the division of labor, the lowest price at which a seller will part with a commodity is not set by the marginal utility or subjective value of the commodity to him. A theory of price applicable to the modern market must not employ the subjective valuations of sellers as a factor in price determination.