Compare most of the prices on Boston Pinball. They are wrong presently considering they go back 72 months or whatever. JD has always been underpriced, so if they move at 2200 now, well that's the price. I sold my JD for 1500 a few months ago and it was sold very, very fast.
JD is from Bally, a wide body in the top 40. It's widely considered to be from the golden age of pinball. I think it was overdue for a correction IMO.