If you have a way to design, produce and maintain a device and platform that is as interesting and compelling to both developers and customers as what Apple has done, and you can do it without any restrictions on what third-party developers do with it, by all means, go for it.
The "smartphone" and similar devices have been around for at least a decade. Apple didn't come up with some magic chip or something to suddenly make them viable, it is their system that is the difference.
Is there a cost to developers? Certainly, but nothing stops you from writing code for more than one platform and if you think you have a killer app but need more freedom than Apple allows, release it somewhere else.
I think what most people miss is that there is a relationship between the control Apple exhibits and the quality of their results; if you don't believe this is true then there are other options for you out there.
I'm tired of hearing about how Apple is "abusing" developers, unlike shared global resources like the Internet and clean air, there's nothing compulsory about using or coding for the iPhone.