I agree with Catfish.....
If a person had an SSK barrel in one of their custom chamberings, where you couldn't get it from T/C or Foxridge, then I think they hold their value a bit better. But, a standard chambering that you can pick up a new T/C or Foxridge barrel for almost half the new price of a SSK barrel, I think it's going to be hard to get close to your investment back out of it. Unless you find a person who it looking for just what you got, and especially if they have a chance to fire it and KNOW it is capable of say 1/2" groups at 100 yards.
I had a used 6.5 JDJ barrel set-up that I sold, and it was fairly easy to sell. I believe because it was in a popular custom chambering & I priced it very reasonable. I believe you can get just a lil' more then regular used barrel price for yours.
I feel the same goes for custom guns, if you can't find someone looking for exactly what you've put together, you'll get maybe a bit more then used gun price for it, maybe. I wish you luck!
Del