What is relevant is that the App Store is a natural monopoly within the iOS ecosystem. As long as Apple has such significant market power (including a substanti

What is relevant is that the App Store is a natural monopoly within the iOS ecosystem. As long as Apple has such significant market power (including a substantial market share, especially as a percentage of revenue, not just units sold) their natural monopoly on the iOS platform will extend to them being a willing participant in an oligopoly. Said state of affairs is the expected outcome of Apple having a natural monopoly and there being only one other substantial mobile OS market participant, who just so happens to also operate a natural monopoly for app sales - albeit a much, much more tenuous one.