IMHO average condition for a '80s boat would be one that was used but not abused. Original sails, some wear to batten pockets but no major rips or repairs; original trampoline, showing its age; solid hulls, chalky gel coat and quality bottom job okay but no major damage or sloppy repairs, no soft spots; straight, watertight mast; proper off season care (e.g. boat on a trailer not on the beach, sails stored inside); etc. Upgrades that would add value to an "average" boat would be replacement sails, replacement tramp, rigging less than 2 YO, upgraded blocks, upgraded/reconditioned rudder system.

There are so many variables that it is hard to say what is a good price especially considering trailer/trailer condition, PFD/trap harnesses, spare parts, time of year, motivation of buyer/seller, etc.

I would walk away from any H16 with soft spots in front of the pylons.