I think that the price of a Nocti 1,2 has not to be put in relation with the list price of the present Nocti 1,0 ... they are different THINGS... If one looks for a 1,0 is surely mainly FOR USE, and maybe you search for a used item (whose price, IS related to the list price of the new)... but if one searches for a 1,2 is mainly for is a collector's item... not that it is a bad lens (I had one many years ago... a sad story...), but if I would have to choose between shooting with an old Nocti at 1,2 or a new Summilux asph at 1,4 ... no doubt for the Lux... and I suspect that for a M8 user if one has the frenzy of 1,2 there is an elegant Voigt that I doubt performs worst than the venerable Noctilux. Collecting is different... I'm very proud of my Thambar 90 (with filter... but no hood
) and wouldn't sell it for, say, 2500 US$ or so, but if sometimes I use it... just for joking.
Collector's market has economics of its own... Thambar is a "limit case", but you have still good user lenses that are valued less lenses that one likes to use for affection only (see, for example, a 50 Summicron of the '60s Vs. a 50 Xenon in GOOD conditions)
But, don't forget : OUR RULE is "ALL old Leitz lenses are anyway usable !!!