In my business I own 5 Dells, including a laptop and the server. I also own an Imac, a Powerbook pro, a mac mini, and a Mac desktop.
The business software we run is Windows only.
The Mac tax MAY be a few dollars more at time of purchase, especially if you go for fancy Apple monitors, and if you pay full retail for Parallels software.
The REAL tax is TECH SUPPORT. $0 for the Mac, $250/mo for Windows.
BTW, at our last professional society meeting, I was flabbergasted to see our business software program being demoed on IMacs running VMWare!
Do you get onsite repairs for the MACs?