The paper analyzes a durable goods monopoly problem in which multiple varieties can be sold. A robust Coase conjecture establishes that the market eventually clears, with profits exceeding static optimal market-clearing profits and converging to this lower bound in all stationary equilibria with instantaneous price revisions. Pricing need not be efficient, nor is it minimal (equal to the maximum of marginal cost and minimal value), and can lead to cross-subsidization. Conclusions nest both classical Coasian insights and modern Coasian failures. The option to scrap products does not affect results qualitatively, but delivers a novel motive for selling high cost products.

In many competitive settings, consumers buy multiple product categories, and some prefer to use a single firm, generating complementary cross-category price effects. To study pricing in supermarkets, an organizational form where these effects are internalized, we develop a multi-category, multi-seller demand model and estimate it using UK consumer data. This class of model is used widely in theoretical analysis of retail pricing. We quantify cross-category pricing effects and find that internalizing them substantially reduces market power. We find that consumers inclined to one-stop (rather than multi-stop) shopping have a greater pro-competitive impact because they generate relatively large cross-category effects.

Motivated by the prevalence of simultaneous bidding across a wide range of auction markets, we develop and estimate a model of strategic interaction in simultaneous first-price auctions when objects are heterogeneous and bidders have non-additive preferences over combinations. We establish non-parametric identification of primitives in this model under standard exclusion restrictions, providing a basis for both estimation and testing of preferences over combinations. We then apply our model to data on Michigan Department of Transportation (MDOT) highway procurement auctions, quantifying the magnitude of cost synergies and evaluating the performance of the simultaneous first-price mechanism in the MDOT marketplace.