Maybe you haven't noticed that the Dell comes with a REAL workstation class graphics card AND it comes with at least three years of on-site warranty -- the latter alone being something Mac users can only dream of.
I also cannot hear the myth anymore that "the Mac comes with the superior operating system". It does not. OS X in average performs crappier and less reliable than 64-Bit Windows, and it also lacks all the features that you want to have in a large network environment where remote administration capabilities and centralized configuration/management are important. Furthermore, OS X is only a viable choice for a certain spectrum of software. Try doing CAD on a Mac. Or running whatever business software your company/enterprise uses on a Mac -- and I'm not talking about Microsoft Office here.
Besides, I really don't know where the price you quoted comes from. That machine above costs less than 1500 Euros when I look at the European Dell website. And when I call my company's sales contact at Dell, I know that I will get a much better deal than when I order it from the website.
But you're right in one aspect: The Mac Pro has a much nicer case than the Dell. But after all, that's all that Apple is about: Nice designs. And the build nice and quiet all-in-one-PCs. But whether you like it or not, Apple nowadays is just one of the many Intel PC OEMs on the market, and despite everything Apple's marketing machinery tries to hammer into our heads, a Mac uses the very same PC component that Dell or Toshiba or Lenovo also use. You pay for the design and the brand - and an operating system that is not the answer to the world's problems, and that is also not everybody's Nirvana.
The only good card I saw there was the Quadro FX 1.5GB (can't remember model#), you can get the Quadro FX 4800 1.5GB for Mac for a similar price I believe.
I don't know what any of the others were or whether they are good or not, the 2D graphics cards category scared me a little though
We can argue for the rest of eternity which OS is better, I prefer OSX and in fact the more I use it the more I love it.
From what I've heard, OSX is common among creative professionals, anything audio/graphical etc..
Windows seems to have a rep for business, although I can't say I know much about that, or why OSX doesn't (if it actually doesn't)
You say OSX performs crappier on average, how do you know this, or is it just your opinion?
If you don't like OSX, there's probably no reason to get a Mac apart from the strict set of hardware they use (OSX therefore runs more stable, although maybe it runs just as well on hackintosh - I don't know).
In the end, the person must evaluate what is most important to them, and decide what computer offers that, or the most of what they need.
I long for the day that may never come, when Apple drop their prices to effectively compete with PCs. Good for me, and everyone else who wants a Mac.
EDIT: I've heard with the workstations that Apple do provide some on-site service, I don't really know though, I just heard someone say that.
Kind Regards