Estimates of the total dollar value of the markets for illicit drugs are valuable for policy making. Such estimates are usually produced by multiplying estimated consumption by price. This paper argues that the relevant price for such calculations is not simply the price of one standard unit. There are substantial quantity discounts for illicit drugs, and there is a distribution of retail purchase sizes. Hence, the average price paid per gram need not equal the price of one gram. This concept is illustrated with calculations for heroin and cocaine.