Microsoft should have executed their launch of RT and W8 like this:
(1) Launch x86 W8 tablet first in the market, let the customers have a more useful tablets that can run all existing applications, and then wait for the "Metro" apps to be developed.
(2) Create a Surface tablet based on Atom to address the battery life and weight concerns for the x86 W8 tablet. For those who wants ipad like battery life and weight, this is the model they can go for. Sell this at price comparable to iPad.
(3) When there are enough useful "Metro" apps already available (including MS own, such as Outlook), then launch the ARM based variant of Surface. This segment should target the $200 Android segment, which should be achievable as they use the same hardware. This will mean RT OS is likely to be free of charge.
You do not want your competitors to be able to entrenched in any price segment. Especially the low end if you want your OS to be the dominant OS, not a niche OS. I am sure some MS executive would have thought of this, but the leadership in MS must have thought otherwise. And this shows MS leadership is making huge business mistakes and there is still no sign of they will change their mind. As of now, the future of MS does not look so great.