And they're charging (as far as I can tell from finding the same/equivalent parts on newegg for the lowest end $2,500 model) 4-5x the actual hardware cost.
While probably far from "best bang for the buck", the 2 2.4GHz is probably closer to the real cost than the other models.
Best 6 cores for the buck seems to be this baby right now, although it doesn't seem to support multiple processors as it is not a Xeon DP.
http://ark.intel.com/products/63697
Yeah, I was just about to post the same thing. What a ridiculous rip-off. A 5770 card? Really, for that price I get a 5770? I just built a new PC for $1500 that blows it out of the water in every aspect but the CPU (I went with an i5 2500k quad-core @3.2Ghz, OC'd to 4.3). I like some things about Apple, I'm typing this on my iPhone, but I would never buy another PC from them unless I needed an ultra-portable laptop. They're just not worth the price tag.
CPU: $260, 3x2GB ECC DDR3: $60, 1TB 7200 RPM HDD: $120, Radeon HD 5770: $120