The question "do Macs cost more" has been around for a really long time and doesn't have a straight answer. It depends a lot on timing, what you're comparing it to and what Mac you're talking about. For instance, I use a Powerbook G4 that cost me about $3000 18 months ago. The only things that matched it in terms of specs at the time (GigE, Radeon 9K Mobility, Widescreen, Size & Portability, DVD Writer) were high end Sony laptops that had similiar sticker prices. As I was moving around a lot at the time and it was going to be my only computer, I figured it was worth it. The current G5s have excelent specifications as well. Dual 2.5Ghz, 8GB max ram, optical audio, PCI-X, SATA, 600W PSU, etc. They start at $2000 and, generally speaking, if you try to match a PC to the Mac's specs (especially adding things like firewire 800, you'll wind up with a similiar price. I'd be hard pressed to find sombody who, upon looking at those specs, would say "that machine sucks"
The problem is that the comparison doesn't go both ways. I'm lucky enough to be able to be dual platform kind of guy and I'm about to build a new gaming rig myself. For $1500 I can get an Athlon 64 3500+ on socket 939, a gig of fast ram, a 6800GT... in short a great gaming rig for $500 less than Apple's lowest-end G5 model. At work we can buy 2.8Ghz Intel based dells for $650 and laptops for not much more than that.
There's a lot more too it of course (If you're a gamer, regardless of price, a Mac just isn't for you). In short, a lot of the specs speak for themselves. Even if you can't find benchmarks (and a lot of cross platform benchmarks are pretty useless), tell your friend to sit down at Apple's site and look over what goes into those Aluminum cases. Operating System preference aside, I think he'll be suprised to see what $2000 buys you from Apple.
-Xy