Domains, like anything else, are worth what someone is willing to pay for them :) There is no magic formula that can tell you what something will be "worth".

Domains, like anything else, are worth what someone is willing to pay for them :) There is no magic formula that can tell you what something will be "worth". IMO/IME speculative domains that have been registered but just sitting idle have very low value. You haven't done anything to prove what kind of traffic they could get, or how they could be useful. Sure, I can speculate some good ideas for "startup.tv", but at the same time I could come up with 80 other domain names just as good for the same idea. "startup.tv" itself has no significant value without something more to it. (this is true for any idle domain name, I'm not picking on yours specifically). You're probably better off just holding them, on the really long chance that someday somebody will really want those specific names and make you a halfway decent offer. In the mean time, throw up a couple of simple pages, maybe some adwords stuff, and let them get a tiny bit of traffic.