Quite frankly, you don't know what you are talking about.
From Newegg:
Intel Core2 Extreme QX9775 3.2GHz LGA 771 150W Quad-Core Processor Model BX80574QX9775
Processors Type: Desktop
Series: Core 2 Extreme
FSB: 1600MHz
L2 Cache: 12MB
Manufacturing Tech: 45 nm
64 bit Support: Yes
Hyper-Threading Support: No
Virtualization Technology Support: Yes
Model #: BX80574QX9775
Item #: N82E16819115044
Retail price for ONE: $1,548.99
Did you happen to notice that the MacPro has TWO Quad Core Xeon processors?
Those alone would cost you $3097.98 for your claimed 3.2GHz. The standard MacPro has TWO of the 2.8GHz Xeon® in the complete system for $2799—the one you claim your home build is still cheaper than—so before you start crowing, add another processor.
The cheapest retail price I could find for the Quad Core 2.8GHz Xeon 1600MHz FSB is $860 so two of them is $1720.
Now, add a 1000W power supply, a top quality 771 Dual socket board capable of handling the 1600MHz Dual FSB, a top quality case, 2GB of good quality FB RAM, optical drive, 320GB SATA HD, a professional OS (not a home edition), etc., and see where you come out.
Trying to build a Dell Workstation with the same specs as the off-the-shelf MacPro resulted in a price $997 more expensive than the Apple and the Dell had only a 1333MHz FSB.
They both sound like great machines.
I can’t afford either one of them so I build my own and I have great working computers.
Unless you’re a extreme gamer, do CAD or video editing, most people who by or build top of the line have way more computer capability than they will ever use.
When I went from P3 to P4 I didn’t notice much of a difference.
I like lots of memory though.