There is no specific formula as far as I know, but yes, of course you can always estimate.

The domain "Groupon.com" was purchased by the relatively new startup for around $250,000 I believe. If they weren't building a multimillion-dollar company around the name, something tells me the domain would not have sold for even 10% of that price.

In the end, any given domain is only worth what someone is willing to pay for it.

Sorry I didn't answer your question, but I don't think anyone can (accurately at least). And if you ever find out, shoot me a PM!