I may be wrong as I don't have the rules under the hand but iirc Apple's rules state that the in-app purchases prices must be set as to not push users to go pay

I may be wrong as I don't have the rules under the hand but iirc Apple's rules state that the in-app purchases prices must be set as to not push users to go pay outside the app. So raising your price may result in a takedown of your app, meaning you have to eat the 30% if you want to stay on the store.