I have a friend who is long term Mac person but just had to buy an HP laptop for a web project. In fact most of the guys I know with an art direction background, who do web stuff, reluctantly have to have both.
The Mac has a great operating system but it's frustrating for hands-on people because many features you may have become accustomed to in Windows are left off for simplicity's sake.
When the Mac works it's fine, but when problems arise I can't find the tools or info I need to fix them -- and I say that because Mac friends call me in to help because using a Mac has deprived them of the hands-on knowledge that Windows users have (cycinics would say because th PC goes wrong often enough).
As for cost -- you know the answer to that ! Now that the Mac is basically a PC in drag it's not hard to detect that the money goes on the pretty case, advertising and the expensive real estate for Apple stores.