We wanted to provide you with the convenience of accessing Emby Premiere from directly within our apps and some of the store terms require us to do so as well. However, this does come at a cost since those store platforms take a significant commission on each sale (most are 30%+) so we are forced to have different pricing with these methods.
Additionally, some platforms won't allow us to choose an exact price so we are forced into a certain "tier".
You can always cancel your subscription created within the store app and then re-subscribe via the web site if you wish.