Not sure I can concur that a custom on a pre-64 is worth more than a Dakota, although I have not looked at the specific specimen.
The reason Dakotas are special is they have double the clientele interest. Interest group 1.: The collector that realizes they are bankrupt, never to return, and that Don Allen made an amazing American product now a collectible using best materials. Competing interest group 2: The group that thinks collectible guns are stupid and that owning assets is dumb, but they want a nice new rifle and a Parkwest is $13,000 and an unused Dakota is half that price.
It's this doubling up on interest that makes a Dakota special. A pre-64 winchester custom is no different then a custom based on a CZ action. It's nothing special for a collector, nor is there anything stopping more from being made. It's a quality gun/action for sure, but there is no blue book of gun values telling you what its worth. For those reasons, I only buy pre-64 or CZ customs if they are over the top and sold for 1/5th of the cost the original buyer put into them. (exceptions: if made by a celebrity maker like Todd Ramirez, JP Smithson, Griffin & Howe)
Not pooping on the un-inspected gun, just saying that you can't compare a Dakota to a custom pre-64 from a nobody.