There are two firms that produce large commercial airplanes, namely, Boeing and Airbus. Boeing and Airbus have different flight control systems, with many pilots preferring one system over the other. The Airbus A380 has a double-deck design that can hold up to 840 passengers and sells for $375.3 million. By contrast, the Boeing 747 can hold up to 568 passengers and sells for $317.5 million. What key assumptions of the supply and demand model are violated in the large commercial airplane market?