Expensive computer are actually Sony computers, not Macs.
Macs are similarly-priced to same-spec Dells or Acers, etc. They just don't do the really cheap models for �300 like you can get with other PC brands with Windows.
If you are, or perhaps have a near relative that is a student at uni, then you can get a good student discount (you need to be connected to the campus network). Perhaps �100 or more.
Should you switch? The question is really why you want to in the first place. If you just want a nicer computer to look at, and Windows does everything you could possibly want, then perhaps it's not worth it.
If you're fed up of having to run spyware-checking apps and anti-virus programs etc. every week just to keep your PC 'maintained', and just want an easier life (and are prepared to pay for it), then go for it.
It'll take your a week or two to really get used to it. Small things. You'll find yourself moving the cursor to the right of a Windows to close it with the "X", when it's a red light on the left of a window on a Mac. Little touches.
The training is very good though. Run by the 'geniuses' at the Apple stores, that are employed and trained to know almost everything there is to know.