MS's TCO is not based on license fees which is what is a pain to begin with. Case in point... you can have 20,000 workstations and not have to pay a license fee (unless SCO wins the lawsuit). MS's ad campaign is like any other business trying to gain new or migrate customers to thier stuff.

Other factors include migration from one platform to another, training, expertise, software, etc., etc....

The bottom line is, if you are willing to migrate from Linux to Windows, then prepare to pay the price...