How can they insist anything at all about pricing on another platforms? Even if somehow it was possible, what a about discounts; are you saying app sellers cannot have platform specific discounts? What about region sensitive pricing (I know about it on Steam where the same item is much cheaper in Bangladesh than it is in the USA, no reson why Play Store can't do it).

1. "Subscriptions must work on all of the user’s devices where the app is available. Learn more about sharing a subscription across your apps."

2. "You must not directly or indirectly target iOS users to use a purchasing method other than in-app purchase, and your general communications about other purchasing methods must not discourage use of in-app purchase."

I think this implies that the subscription must be the same for all devices and you can't treat iOS differently. Pretty sure having a lower price if you subscribe on Android would violate that second clause.

Another piece of evidence: on the site, on June 2014, they mention raising the price to 13 Euro to make up for the 30% charge. I don't think they raised the price for web subscriptions at that time.