But Microsoft IS selling the "cheaper one". This is not to say that there will be no other Windows 8 tablets of course, Microsoft is licensing the software out to third parties (I think I saw a Lenovo tablet with Win8 advertised the other day).
On the other hand, MS's version has a 1080p screen instead of 768p, it has USB 3.0 instead of 2.0, not sure if the lenovo has video out or not, not sure if it has a keyboard attachment or not either. All things that add value (being able to run a beamer off your tablet instead of needing to schlep around a laptop aswell just to do presentations is a big QoL boost). Not to mention the Surface Pro having a quadcore IB instead of an Intel Atom single/dual core.