Hate to tell you, the answer really is: depends.
Depends on condition, stainless or blue, wood or synthetic stocks, barrel length, modified, upgraded, scoped, not scoped, but with scope base, type of breech plug, if gun comes with accessories, etc.. I'm sure you see where this is going. Your best bet is to check the classifieds to get an idea what a sidekick that matched the one you have is selling for or sold for.