Apple is right to insist on ONE, trusted purchasing method on iOS.
Apple is right to allow bypassing that using the Web—which remains open and uncontrolled.
Apple is right to demand a cut of the money from companies making money off the iPhone and iPad and the store infrastructure that Apple created and maintains (and which were not free to build). Apple processes the payment, provides post-sales customer support, and offers a user-friendly funnel for other companies to make money—subscriptions included.
And Apple is within their rights to set any amount they want. Competitors can take it or leave it.
But I have to feel that Apple is wrong about the amount. How about 10 or 15% on subscriptions? Keep the 30% on app sales, but take a smaller cut of services/renewals. I’m not shedding a tear for Microsoft, but the numbers just feel high to me.
(I realize that would mean back-end complexity resulting Apple’s cut for IAP varying: some IAP is a subscription, some isn’t... and some is a grey area, like virtual currency that can be exchanged for essentially app upgrades. So be it. Apple can write policies and face that complexity.)