I'd love to sell MY puny domains for what they value them at! Here's one I only use to host a few mp3's and such:
Musicalgearbox.com Valuation $3,377.92
I've got another domain I've used even less that's "worth" more, so I had an idea - I typed in THIS fantastic domain name:
B8fj38fgr443.com Valuation $4,301.12
and of course it doesn't exist, it's just my fingers hitting the keys in as random order as I can...
So I figure if I register 300 domains like that, I'll be as rich as Mac.
My guess is this thing does a simple web engine search on the domain and gives higher dollar values for domains (like absolutewrite.com) that give a lot of hits. There's surely a little bit more to it than that, since B8fj38fgr443.com gives ZERO hits on Google, but whatever.