Spotify Premium account price on App Store

As you may already know, Spotify started sending out emails to its customers to stop subscribing to the Premium account through iOS App Store's In-app Purchase mechanism (which costs $12.99) and subscribe using Spotify website (which costs $9.99). The reason behind this difference is that Apple charges 30% of the purchase price as its noted here . The purchase price of Spotify Premium through App Store is $12.99. But this doesn't make sense to me. 30% of $12.99 is approximately $3.9 so Spotify will be making $9.1 instead of $9.9. Is the 30% calculated after the developer states its intended price? i.e. Spotify says that it wants to earn $9.99 with each purchase. Apple says fine, I'll charge $12.99, have $3 (which is 30% of $9.99) for myself and you can have the remaining $9.9. (I don't believe this is the case.) Or Spotify is actually selling its Premium account cheaper through App Store? What I mean is that in order to earn $9.99 per purchase, one should charge approximately $14.28. Can someone please clarify the situation? Thanks.