Personally, my response to this is...
How often do you need a new machine?
Back when I used to use PCs at home, you always had to keep upgrading them, because they always started to struggle, especially with games.
My first Mac was a Powerbook G4, it's about five and a half years old now and I still use it as a laptop just fine. Then I bought a Mac Pro a couple of years ago, and I don't see myself needing to upgrade from that for quite some time.
So yeah, they might be high prices initially, but then I feel I've gotten a lot of use out of them. I don't really see the need to be upgrading on them all the time, unless you are the type of person who has to have the new Mac Book Pro/Mac Book/Mini whatever....
Your post actually got me thinking more so than I was
The MacBook I currently have is a 2Ghz Core Duo. It is still functioning (after a free keyboard replacement, RAM upgrade, 2 HDD upgrades, battery replacement and power adapter replacement

) even though I think the wireless has taken a turn for the nearly-b0rked

So I'm back on ethernet now.
In the middle of 2006 it cost £899 (£850 with a student discount) which didn't seem all that extreme considering very few laptops had a Core Duo and no PC laptop could touch the 4-6hrs battery life.
So why did I get it?
Latest CPU technology
Long battery life
1 Year Old OS (Tiger) as opposed to a 5 year old one (XP) that just generally interested me
Highly portable
Decent enough price
Everything Mac OS X/iLife brought to the package
The only thing for me, personally, that hasn't changed is the long battery life. In the current MacBook/13" MacBook Pro models:
Old CPU technology
<1 Year Old OS (Snow Leopard) as opposed to a <1 Year Old PC one (7)
Netbooks are the new highly portable
Base price is going up
Whatever your opinion on Snow Leopard vs. 7... they are much closer in terms of awesomeness than XP & Vista ever was to OS X Tiger or Leopard.
With iLife I only really use iPhoto, and Apple have done some things to annoy me that have made me switch to Picasa.
So while I could spend £1000 on a new Mac portable. I could just as easily get a £250 netbook and build a £750 desktop PC or any such combination for the price... even save the money
