He calls Apple a rare example of a consumer-focused business with highswitchingcosts because customers are attached to its music, photo and other applications.
Though the answer to this question can vary from one region of the country to another, the most plausible answer is lack of competition on the supply side and highswitchingcosts on the demand side.
In the operating-system business, expanding the market the first rationale for less-than-monopoly prices might be wise because the highcosts of switching from Windows and Windows-based applications to any putative competing suite of products tends to lock new users in.