Like most Fords - those two are horribly over priced. Just cos the actual GTHOs are the best falcon (of a an extremely poor bunch) built by a long way and the fact that they didn't make many doesn't necessarily mean its actually any good or even collectible
Plus they are fugly
If I was ultra rich I would buy all teh GTHOs that ever came up and burn them for my amusement................. yes, yes I would 
Nick, performance, handling, looks.....none of these have anything to do with why some cars are considered collectible. There is always something cheaper that is faster, handles better, or looks better. Plenty of the rare exotics fetching big bucks are woeful road cars with dubious track success. As an extension to that, no modern Falcon GT will ever fetch the relative prices of the HO. They are much better cars, but again, that's irrelevant.
I'm not sure the Phase III is necessarily the
'best' Falcon either.