I paid way too much for my '90 ($900) but I had the money so I didn't care.

A '90 Mighty Max locally was advertised for $1,200.00 / offer, in about the shape you're talking about. Without pictures it's hard to say, but my guess is between that $900 and 1,200 mark...maybe a bit more if it's really clean.

Let's see what others have to say.