I’ve always believed that prices have increased largely due to expanded scholarship for some of these references.
You could argue social media is driving this from a demand side, but I think resources like OF, Fratello, and Moon Watch Only have largely gotten rid of any information asymmetry for these references. People are more comfortable paying $10k, $20k, $100k for a watch when they know the watch can be verified to be what it is (serial#, dial, case, pushers, etc).