Book contests...are they $$worth$$ it?

Here's my question: are all these book competitions (Ben Franklin Awards, Indie Awards, Writer's Digest, etc.) worth the entry price? Say you win, does that actually sell books--and if so, by what mechanism (press release, etc)? I'd love to hear from someone who's won a contest and seen extra sales as a result. Or from someone who won, but didn't see tangible results...