I was offered 4000.00 for my 1989's awhile back and turned it down. We can all agree Belle's are getting harder to come by which to me, factors into overall value. Of course it's all relative to what a person's willing to pay for them. I don't know if there's an actual "Belle Value Guide" out there. If there is, I'd like to know about it.
I remember there's someone within the forum that keeps track of what heritage Klipsch speakers are going for. I cannot remember who it was.