Sounds like you have a #5 or worse. These figures were found at:
http://www.vmrintl.com/cctm/coll_frame.htm
Remember, different areas of the country, along with other factors, have a bearing on prices .... along with how much YOU really want the car ....... Good luck and I hope he came through and took your $500 offer ....
#5 #4 #3 #2 #1 2dr Hardtop 450 1525 3050 5200 6900 2dr Convertible 725 2750 5100 7025 9300