Well, here are some examples:
http://buck-184.com/buckmasterebay.html
Depending on the condition, the markings on the blade, and the specifics of the model the price range can be anywhere from say $60 to $2000. Note most sell for well over $60 and only very unusual ones should sell for over say $600.
The typical price seems to be about $200 but that depends so much on condition and what comes with it... without more info, I can't give you specifics.