It's hard to say. The dt sabers for Vader and ben are quite rare. The key is what is it worth to you more than what crazy market place price says these days. While a dt is a special piece, sinking tons of cash into them may not be the best investment for your collection. I have a dt Luke and a broken up dt Ben, if a Vader fell into my lap I would love it, but for me I can think of a lot of other items I would rather have that I can spend the same dollars on to get. Having said that, a price range of $2k-$5k is what I would expect; but again is $2k for one piece going to bring you the most happiness is what you need to consider.
I have caviar dreams and McDonald's pockets