I do agree with your general point. Your characterization ("Maybe some labs that wanted a unixy OS and, again, convinced their purchasing officer to buy a Mac

I do agree with your general point. Your characterization ("Maybe some labs that wanted a unixy OS and, again, convinced their purchasing officer to buy a Mac Pro?") is a little off -- where I work, MBP's for laptop replenishments are treated exactly the same way as Windows systems, you just tick a different button on the order form.