I was going to buy one recently, but then the new Sigma 35mm 1.4 caught my eye - decided the 1.8G 85mm was suffient for my needs, put what I saved on the 1.4D toward the 35 1.4, happy out.
I'd say $800-850 in mint condition. Make sure there's no crack on the plastic M/A ring selector, no nicks on the elements, and the filter thread is not bent. This is the only Nikon lens that I've sold twice and kept coming back to. I even sold the 85 1.4G and went back to the D, as I like its rendering a lot more.
Also, check the M/A selector ring carefully. Look for cracks (as mentioned above) and check the movement. Rotate from M to A and back. There should be no play, and it should snap to a click at the end of the rotation. No over rotation. Does it affect functionality? Probably not. But, to me, it is a rough indicator of how the lens had been handled and used.
Ask how old it is (better yet a receipt), the early versions of these lenses will be 14ish years old and many will have had pro use by wedding photographers.
You could just buy a new modern sigma 85mm for the same price of course...
As everyone else has suggested, $700-850 range depending on condition. Picked mine up two years ago in like new condition from a member on here for $900. A truly remarkable lens, love using it with my D700. The bokeh it renders is absolutely beautiful.
indicator of how the lens had been handled and used.