Yeah, I that's what I feared, but thanks for checking. You didn't say about Windows Web Server in a domain environment, but assuming the worst, and all servers would need to run the Standard edition, that would be $145 x 5, or a whopping $725 per month just to license Windows! That's not including whatever cPanel's fees will be per user!
After reading the SPUR some more, I'm interested in the per-user Subscriber Access License (SAL) model as a more cost effective option for getting started. Please correct me if I'm wrong, but it looks like you can run Windows Server Standard on as many computers as you want without any extra fees as long as you pay about $3.50 per domain user.
This brings up a technical question about how cPanel Server Suite adds "FTP Users" and "Password Protected Directories" in IIS. Do either or both of these options work by adding additional domain users (and thus would have to be reported in the SPLA reports)?
Thanks!