Server Hardware Vs. Workstation Hardware

I am Trying to get a req approved to purchase a Dell server when I got hit with “Can’t you build a machine for cheaper than that”?
I tried to explain why it would be a better investment to buy a file server rather than build a workstation and load Win2k server.
But… They want to see articles.
Does anyone know where I could dig up an article explaining the reasons you would NOT want to use a clone for a file server…