John
Not one VALID study.

Mayor of R'lyeh
The only study that is reasonably modern was funded by Apple and was disowned by everybody involved once that fact became public. It seems that if it wasn't tainted in some way somebody would have defended it. All of the other studies show that Unix has a higher TCO than any other OS. Maccies are constantly bragging that MacOS X is Unix. When they cite these studies they are declaring that MacOS X has a higher TCO than Windows.

Lastly, anybody with even a glimmer of knowledge about TCO studies knows that they are only applicable to specific situations. The notion that a TCO study at Place A had result X thus we will find result X in all situations is silly and not supported by reaity.