the truth is that anything (not just domain names) is only worth what you can persuade someone to pay for it,
and the less established a market the less stable prices are.
IMHO it is almost impossible to value a name without knowing who the potential buyer/s is and how desperate they are to get it.
What makes a .biz different from a .com other than the different letters and meaning?
The .BIZ domain is currently the 7th highest domain used in the world (627k of them). Because it is so new it does not have much branding or public cognition. You will need to hold the domain a few years before it is worth its full potential. But I have no doubt that .BIZ will be lower then 7th spot by then.
When I eval domain prices I start at the .COM and work my way down to the TLD the owner has. It all depends on the domain and how much potential branding it has built into its self. The ultimate eval tool is how much background traffic does it generate. That is one of the strongest indicators.
Did I ever mis-read a question! My answer re com vs biz was referencing the meaning.
Lisa is right, everything (speaking from a US perspective, anyway) revolves around the COM, which means everthing else is worth substantially less. In limited circumstances, I can see .info having appeal, like travel.info -but the others often just imply you missed the COM on the first go-around.