Check the marine trader web site for boats in your area. I suspect that the prices will be more realistic than nada since they reflect actual boats for sale rather than averages.
Agree with the comments on NADA...check your local classifieds or Trader for comparable boats. It might help if we knew what you had. I'll give you $100 for it and pick it up next weekend
I don't know why Nada even bothers...their numbers are obviously pulled right out of someone's a$$. I believe they say my boat is worth around $800...if I could find 'em for that price I'd buy 20 of them...