Have you tried the FAQs?
I think that's the crux of the issue... answering the question, "what is your domain's value and where does it come from?" Unfortunately, using comp sales is not a guaranteed indication of value because there is always the possibilty your name will not sell. The 'value' of iReport.com was probably relatively low compared to it's ultimate sales price until the right end-user with the right motivation and budget came along. And there's no guarantee that the 'right' end-user will ever come along for a lot of your fresh registrations (or even for decade old quality generics!). IMO, the value of
anything is what you can sell it for right now - ie, liquid value. LLL and LLLL.coms have 'value' because there is currently a relatively liquid market for them. Generics have inherent value because they generate click revenue and those kinds of names are in high demand.
There is always the possibility that some end-user will see great value in your domain, but if no one ever does, (and assuming it doesn't generate it's own revenue) your domain is ultimately worthless.