If a durable-good monopoly can use either of two technologies whose properties are known to consumers, the monopoly … uses only the technology with the lowest average cost at low levels of production. If consumers only know about … technologies occurs only if consumers are not fully informed about both technologies. …

Where consumers have imperfect information about specific firms' prices and lack information about the market, firms … (but not all) consumers have perfect information, single-price equilibria are impossible. …