If you're unfamiliar with linux, then it costs $0 only if your time is worthless. Plus, there isn't a good ASP.NET implementation for linux. Mono's attempt is imperfect.
You're right, of course. Really, if it would cost a person only a few hours to switch to linux, or a couple of minutes of productivity per day, it wouldn't be worth it.
But there's the possibility that someone would gain productivity by using linux.
It IS confusing, but it's confusing on purpose. It's meant to convey complexity and seriousness. Look at all the parts and functions -- you'll need to talk to an experienced sales rep and follow up with some service engagements from our consultants.
Try Windows Server 2008 XLT, now with 20% more server goodness. If you like that, you'll love Server 2008 XLT-VX with all the server goodies you've come to love and 10% more virtualization!
I like their pricing for Windows Web Server 2008 -> $469.
Pretty good for startup if you choose ASP.NET.