The heads don't look too bad, Mark. They need to be cleaned to be sure but it looks like the guides are the bigger issue. Put a belt on it for the fellow, clean it up and see if he can get $500- $600 for it. If it's in working condition with a new belt and a cleaning, then it should fetch that. Just tell him to be honest - someone may want it for a project, though I'm not sure why. There are much stouter and desirable decks from Teac and Tascam out there - some not too far from that price point. Daily driver 2300s, 3300s, 6300s, etc. can still be found between $600 - $800.
I just think between what you and I saw, unless he wants to sell it as is, parts only, he's leaving a little bit of money on the table at $400.