Sure the claim that an artifact like a painting is valuable because it’s rare & famous is somewhat self-reinforcing, I agree. I also think it’s fair to call it circular in the sense that people investing and making a profit when they re-sell will cause more people to want to invest, and will drive the prices of collectibles higher. The value of a collectible is a social construct rather than a reflection of, say, skill or materials or cost to make, and so normal economics doesn’t really apply.
I’m not quite following the rest of your logic. Rare collectibles don’t often lose value after 70 years, there’s no reason I know of to suspect the ‘age-wealth point’ of the collector is particularly relevant. I’ve never heard of historicity nor seen anything collectible accrue value as a percentage of age, I don’t think markets for rare paintings work like that…? The idea of paying millions and millions for a collectible you can’t really use is foreign to most of us, so yeah it’s really weird and I can understand the feeling that it must be self-reinforcing.
I guess I’m maybe not even arguing for or against any of this, but maybe saying that given that markets for rare things exist, it does make sense that very rare+famous things bring higher prices, and that people who have money for this kind of speculation might see investment opportunity. I agree the “value” and market for these things is circular. All of the value comes from the “proof” that something is rare and collectible, purely from the story.
All this does apply a little bit to consumer goods, of course. We often have to remind ourselves that capitalist markets price things according to supply and demand, not necessarily to cost.