The thing is to have someone in your locallity that needs them. You seem to have that. Ask him what he considers fair pricewise.

My feeling is that four complete doors no less than fifty apiece. They are in reality worth more but once again the demand has to be there to get it.

Quickly trying craiglist might help establish if there is other interest locally. In my area for instance there is pretty well zero demand at this time. You could ask for his complete doors as part of the deal to salvage usable regulators with motors etc out of. Never any harm in having them around. Or saleable as well if good.