You're not going to like what I say: My idea of what it's worth is a waste of time. You have to value a site based on what you think you can make out of it, what effort you estimate is needed and the risk you see of that expected profit not materialising.
In a detailed post elsewhere about a month or two ago, I gave an example. I examined a site that others were talking about and explained this point in more detail. I illustrated what I would do if I was planning on buying it, looked at how I'd monetise it, how much of profit I estimate (and why) and then came to a value conclusion. If anyone remembers that thread please drop us a link.