E5-1650 - $550
2 Firepro D500 - $490 a piece ($980)
12 GB DDR3 1866 ECC - $180
Motherboard - $160
PSU - $90
256 GB SSD - $140
= $2,100~
Apple Mac Pro cost - $2,999
I made this account for the purpose of responding back to you. Your math is very much off, or you're getting some very good deals.
Now, I like the truth, and backing up what I say. It sounds like you're a DYI person who loves building his own machines, right? If you are, you should be familiar with
www.pcpartspicker.com - a website that finds the lowest price for most computer parts, and checks compatibility between them.
So I decided to go there, and try to build one. What price did I get for an entry level MacPro equivalent?
$3,800
What parts did I use? Go
http://pcpartpicker.com/p/3fZn2 and see for yourself.
Now, is this a match-for-match to a MacPro? No, it is not. It doesn't have a motherboard with ECC Ram, and the Ram isn't ECC. The motherboard might not fit in the case, and the motherboard might not handle the Thunderbolt cards, and the power supply might not have enough wattage. Plus, the D300 isn't as good as a W7000, but I just did a quick job, and not too much research on this.
But I'm sure my list is a whole lot closer spec-for-spec then your list.
(I'm assuming you're trying to spec the entry level machine, the D500/ W8000 is in the mid-range. If you want to include the W8000, add another $1,000 to my total).
Unless, of course, you're willing to cite your source, ideally from pcpartspicker.com , so we can all look at your sources, build our own MacPro, and undercut Apple.
(Note, I do not work for pcpartspicker.com , I just really like their site).