Evaluating site traffic for appraising a site

[gph]

Folks,

What are the "ballpark" numbers for figuring out the value of unique visitors to a Web site, when other factors such as site content, domain name etc. are factored out?

I am looking for something along the lines of "if you're getting xxx visitors a day, that traffic is worth $xxxx if you were to sell the domain name that is getting the traffic".

I know this will vary, but I am looking for rough estimates so I can judge the asking prices of domains for sale accurately.

Thanks

gph