finding good type in domains?
 

This is another question that i have had about Search Engine traffics and domains. While i've been searching for keywords/phrases that go hand in hand with my niche i've found a lot of phrases that could easily be dot coms. Only thing is that I don't want to go out buying a lot of domain names and then they turn out to be worthless. For example some of the phrases that I've run across could easily be domains: REDWIDGETS.COM but I can't determine if these domains would be worth the 15 bucks that directnic charges. Do surfers usually type a phrase + .com before they go to search engines? Is this a waste of money or a venture that might be worth looking into?

P.S. most of the phrases that I found that could be turned into domains all got less than 1000 searches per month. Any insight on this is appreciated.