I sent in my Jester to Spyderco because I noticed rust on the Liners and Screws, and after a few emails with Charlynn, I sent it in. After around 3-4 weeks, I got a package back from Spyderco with my Jester in it and the rust gone. I don't think they figured out what had happened, and just recommended I keep it oiled which I do now. Price range, I can't help you with that as I don't think it would be covered under warranty and might depend on how much rust/how bad it is/if it even is salvageable.
One thing I have seen though, with pinned knives is if you are willing to have replacement scales made with screws instead of pins, it is possible to just pry it apart, take the pins out and replace them with screws when you are putting it back together, but this would definitely void warranty.