Also take in mind that TFS requires a LOT of more horsepowers from the server hardware. And at minimum one windows server licenses ofcourse.
Best practice, as our company followed, is to use 2 servers: front-end (with integrated sharepoint), and a dedicated sql server in the back-end (we use an enterprise cluster). TFS can be installed on 1 machine, but should not.
In comparation, our svn server is installed on a virtual linux server with 256mb ram and 1 cpu, and is still several magnitudes faster when doing common tasks like checkout-all. The virtual hardware was the lowest vshpere could assign! Disk is fast though (SAN).
I whould suggest that TFS requires dedicated hardware for atleast $5000, while svn server (on linux) can run with any hardware which is obsolete for current windows based os.
