Besides what Space cowboy said below:
What kind of a CPU is that? If it's a quad core XEON at 3.2 ghz you're looking at around $1k for that part.
Add another $400 or so for 12GB of ECC memory (which the mac pro uses).
$400 or so for a systemboard supporting QPI.
$850 or so for that video card.
We are well over your $2500 figure and we haven't even looked at the hard drive, USB 3.0, FW800, case or PSU.
Clearly you don't understand what a workstation really is. If you compare the mac pro price to other workstations on the market it is VERY competitively priced.