In some cases, such as this one apparently, it means selling on iOS is no longer a good value proposition. Yet this is little different from the real world. If a mall decides to up the rent for the retail space you are using and that price is beyond what you can afford, then you have to move. Thats buisness.
I'm not saying Apple's approach is perfect, but its also not as evil as some are claiming it to be. Remember, Apple's primary focus is providing a positive experience for the consumer, and many of these in app subscription and purchase policies are meant to make sure the customer gets treated well. The developer is less important to Apple than the consumer (so long as ther are enough developers to satisfy the consumer and right now that appears to be the case).
Apple made its choice and as a result its alienating a few developers, who can now jump to other platforms. Apple's bet seems to be that such a policy change is worth losing a few developers over. We'll see how it plays out. Its also possible that this is an unexpected consequence of the policy and Apple will end up modifying it based on feedback, preassure, etc. It's not like these rules are written in stone.
Beware of all enterprises that require new clothes, and not rather a new wearer of clothes. -- Henry David Thoreau