Inflation and its actually cheaper .If you recall, all the analysts were predicting *starting* prices from - The iPad blew those expectations out of the water, and forced several prospective competitors to restart the designs, by starting at
Surface has it desktop "cousin" wich is also capable of metro apps.There were, at release of the first iPad, more iPad-native apps than there appear to be for Surface. It *also* had access to a thriving ecosystem of apps (those pixel-doubled iPhone apps). The experience through the iPhone apps wasn't anything special, but it could still 'get the job done' while you waited for the the iPad version.
That's a fall-back option the Surface doesn't seem to have.
350million PC sales worldwide a year, 80% MS (conservative estimate) windows 8 so within the year it would have more user then ios has now, and if I include the unlicensed its a lot faster that high.