Traditional micro-economic theory assumes that consumer preferences are independent of market forces like supply, demand, and price. However, this assumption is inconsistent with psychological research on commodity theory (Brock 1968). This research has found that scarcity enhances the desirability of experiences and objects. Two studies were conducted to test the possibility that these scarcity effects on desirability are due to a tendency for people to assume that scarce things cost more. Consistent with this hypothesis, study 1 found that scarcity increased the desirability of art prints only when subjects had been primed to think about the expensiveness of art prints in general. Study 2 further supported the hypothesis by finding that scarcity enhanced the desirability of wine only when subjects did not know how much the wine cost. The economic, marketing and research implications of these results are discussed.