Why does apple have to deliver its service to a 3rd party at cost price? It can charge what it likes. If they charged 60% and all app developers moved over to

Why does apple have to deliver its service to a 3rd party at cost price? It can charge what it likes. If they charged 60% and all app developers moved over to google the market would soon follow or Apple would change. The cost of the service for Apple is irrelevant in this court case.