Well, because PC’s crash, the OS is garbage, and they get viruses, which cost company’s a LOT of money. Not to mention the cost to have a tech guy working for you just to maintain things, or a consulting company that you use…either way expensive (not saying you NEVER need one for Macs, but a lot of things are just easier to setup yourself).
Even compare Safari to Internet Explorer…it’s just a joke.
There are also a bunch of articles about how PC’s are actually more expensive in the long run when compared with PC’s.