When two prices are charged, people paying the higher price (often in the United States) believe that if the firm were forced to charge one price, it would charge the lower one. Unfortunately, that is not always the case. Sometimes mandating a single price results in just choking off the small market, rather than lowering the price in the large one.

—from Leveling costs worldwide is not cure for drug prices (DemocratAndChronicle.com)