According to Apple's In-App Subscription Rules,
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.
The questions are:
If I don't link my webpage (where the user would be albe to subscribe without going through iTunes) directly but I just mention that it is possible to subscribe via my website (and perhaps I write my website down but I don't make it clickable), would Apple reject my app?
What if I also mention that if you subscribe via the website you'll get a free month of subscription, but again, I don't provide any automated way to go to my website?
What if I mention that if you subscribe via website the price will be lower?