Any amount listed in a book regarding gun valuations has to be taken with a grain of salt, you can look in 3 different price guides and get 3 different prices. The compilation of a book can be months ahead of the printing date... a lot of things effecting pricing can change before a book hits the stores.
Real market prices can vary greatly by geograpic area and conditions... I think a better gauge is a composite of the selling prices seen on the gun forums, what people are paying on the auction sites, gun shows, gun stores, etc. You'll start to get a feel of what a realistic price range is.
I own a 24-3 Lew Horton too, and if you've been following the prices of what factory N-Frame round butt combat grips, the grips on our guns alone are worth between $100 - $150, and that's something that the price books don't take into account.