They're not charging per GB of S3 or whatever. It's likely a fixed(ish) priced contract that basically covers their cost of building a complete region. So the pricing doesn't really compare.

Basically, AWS is all public cloud, none of this private cloud nonsense... until you come along with a $600MM check and then you can have a private region all to yourself!

Someone's still got to pay the energy bill and for new servers to account for growth.

I don't see why they would throw at their current billing model for something else.