Ummm
I went to the HP site and came up with $4695 for a Z820. Dual E5-2620, 16 gig of ram and AMD FirePro v7900. 1TB 7200 HD. And it's an LGA2011 based system opposed to a 1366 solution on the Apple side.
Again I'm not playing favorites but there are a ton of hackintosh sites. Why would there be such a market for this info if Apple was superior in price/configuration?
ADDENDUM:
Because I'm a curious sort I sourced a MacPro with the above spec and came up with a figure of $4398. The GFX solution was an 5870 which is about $200 cheaper than the FirePro v7900. Taking that into account you are talking a $100 delta. I still haven't been able to come up with two factor difference in price between HP and Apple offerings.
For a third option I decided to spec a hackintosh w/ a Gigabyte Z77 MB that by golly supports Thunderbolt (Apple doesn't on the MacPro). Only did a quad-core xeon, but added 16G for a total of 32G ram and a GTX580 GPU. Build was ~ $1400.
