I recently traded for a mint condition BF. The seller originally wanted $2500 for it, talked down to $2200 before settling on a trade. Somewhere between $2000-$2500 depending on how nice yours is and how quickly you want to move it.
BF is a fantastic game, probably Sega's best. Doesn't even feel like a DE/Sega with how huge and impressive everything on the playfield is, comparable to a loaded B/W.