"a platform that is pretty much the other biggest half of the market and in an explosive growth market in general."
this is the crux of it tho. Apple provides more than just a payment processing system. they provide access to 100+ million users who can pay with a single click, and more importantly have shown their willingness to do so.
This is what they are charging 30% for access to.
Up until now these services have been getting a free ride, and they all know exactly how valuable access to that market is worth. They are absolutely willing to pay to access that segment, now we are just seeing the beginning of the negotiations.
Apple says 30%, all the companies reply with 'we cant afford that
this is how business works. if you want a prime retail location, then it will cost you premium fees, and you make it up with greater customer traffic.
so a better analogy might be:
each paycheck you get $1000. you can keep that (ie not put your app on the iDevices)
or instead each paycheck will be $700. but you will get three times as many paychecks.
Which one do you choose?