It isn't worth anything. Just bring it over to me, and I'll see it is disposed of properly, that way you won't have to worry about harming the environment.
Seriously, it really depends on condition. Even in good condition, there are too many variables to make much more than a s.w.a.g., so, my s.w.a.g. is somewhere between $7,000 and $25,000.
While that sounds like a cop-out, it really isn't. Sight unseen, one man's "really really good" condition is another man's "take it out back and bury it" condition.