Though as a thought experiment Apple is like a wealthy landed gentleman who sets up a well maintained outdoor market for the tradesmen to bring goods and the lower classes to buy them. If Apple owns so much land they are the only ones capable of setting up a large enough market, maybe we should regulate that gentleman's fees to the tradesmen? By virtue of people's need to be fashionable and the enormous cost to develop a smartphone and OS, Apple effectively controls enough "land" to warrant regulation. I don't know...
Finally, this rationale also it seems causes a dilemma with B2B relationships. What if your market is quite specialized? Are you a "monopsony"?