I am not an expert in auction dynamics but whilst teh Dato is produced in relatively small numbers, it is not seen as a rarity. It's been in production for 10 years now and you can always find a Dato if you are willing to wait three months.
In my view, rarity is key. This is a marketing strategy that PP does very well. Should Lange decide to stop producing the Dato, I am sure the resale/ auction price will be improved. I personally think that Lange's approach is to create a classic/ iconic watch rather than a rare watch.
rabi'