[dwaite]

Both sides run services which have costs, the customer acquisition needs to take into account the potential profit of having the customer and not just raw revenue.

Maybe Apple clears 15% of the user's purchase price after credit processing, tied-in platform development costs, customer service/hosting fees, and the 70% payout to HBO, and HBO clears 15% after licensing, hosting, app development costs and the 30% fee from Apple.

In this case, HBO would be motivated to have a website sign-up to raise their 15% to closer to 40%, and Apple would be motivated because otherwise they are negative for the lifetime of the subscription.