I bought one for $400 without the preamp. The guy that sold it to me could have gotten much more if he had a preamp pedal because all the calls received were from guitar players that were wanting a leslie to play guitar through. With preamps I have seen them priced at $1100 but I think the seller was smoking crack.
I have a 122, a 3300 and a 860. I use the 860 a lot for local rock gigs because it rides easily in the back of my Chevy HHR. It lack some low-end but the wonderous sound guy is able to help either by using EQ or that BBE thing ... or something ( I just play). It is loud and good enough for rock and roll. I wouldn't use it on a Jazz gig.
I'm a big fan of the 860.