I wonder if the reason that they don't offer less powerful, cheaper machines is that Google itself does not use such machines; You aren't "scaling like Google" if you are not using the same types of machines as they use in their actual architecture.

Edit: You guys are right, obviously, they will almost certainly offer slower, cheaper machines at some point (even if this wasn't part of their original plan, there is a visible demand, which should motivate action). However, my real point is that I'm guessing that this initial roll-out does map more closely to what they use themselves than whatever their eventual full catalog of offerings looks like.