Price variation for identical cars at the same dealership is commonly assumed to arise because dealers with market power are able to price discriminate among their customers. In this paper we show that while price discrimination may be one element of price variation, price variation also arises from inventory fluctuations. Inventory fluctuations create scarcity rents for cars that are in short supply. The price variation due to inventory fluctuations thus functions to efficiently allocate particular cars that are in restricted supply to those customers who value them most highly. Our empirical results show that a dealership moving from a situation of inventory shortage to an average inventory level lowers transaction prices by about 1% ceteris paribus, corresponding to 15% of dealers' average per vehicle profit margin or $250 on the average car. Shorter resupply times also decrease transaction prices for cars in high demand. For traditional dealerships, inventory explains 49% of the combined inventory and demographic components of the predicted price. For so-called 'no-haggle' dealerships, the percentage explained by inventory increases to 74%.