Apple has changed its developer guidelines [German language] relating to the pricing of In-App Purchases and Subscriptions on the App Store.
Previously there was a requirement that any and all purchases or subscription had to be the "same price or less than it is offered outside the app" but this has now been removed.
I have confirmed that the change has occurred.
Here is the old wording:
11.13 Apps can read or play approved content (magazines, newspapers, books, audio, music, video) that is sold outside of the app, for which Apple will not receive any portion of the revenues, provided that the same content is also offered in the app using IAP at the same price or less than it is offered outside the app. This applies to both purchased content and subscriptions.
Here is the updated wording:
11.14 Apps can read or play approved content (specifically magazines, newspapers, books, audio, music, and video) that is subscribed to or purchased outside of the app, as long as there is no button or external link in the app to purchase the approved content. Apple will not receive any portion of the revenues for approved content that is subscribed to or purchased outside of the app.
This means that companies such as Amazon or Netflix will continue to be able to offer content for iOS apps without having to make said content available through the app (and without having to give 30% of the purchase price to Apple). It does mean though that the likes of Apple will need to remove the link to its online store from within the app.