Thank you :) Today my son found, somewhere in depths of my old toolboxes, a small metal plate with an eagle and "born to ride" inscription - something I took from my first serious motorcycle. It's objective value is about zero, but it is unique and valuable in non-monetary terms. Valuable only to me.

Cult classics are similar in that sense - items that have meaning to only some people, but those chosen few will gladly give $500 for the item that many other people would consider, well, rubbish. Soo... the scarcity I had in mind was simple matter of stuff that is necessary to live (water, food, shelter), but has no special meaning on its own. Oh, it can, of course:

https://www.mostluxuriouslist.com/top-10-expensive-bottled-waters-world/

but that water is not expensive because o scarcity - it is expensive because of uniqueness. To me it's not quite the same thing, uniqueness is scarcity in some respect, but it has slightly different tone - scarcity is about things you need, and uniqueness about the things you want. I preemptively agree that the boundary there can be blurred sometimes :) And I also think you are totally right, people will inevitably find something to give value to... because psychology. Maybe because in our culture we're taught to never be satisfied, it would be counterproductive to our economic system... :) And even if/when we have molecular duplicators, and we can copy Mona Lisa atom by atom, and we had exact copies of the painting, they will be worth $100. The original will remain exactly as expensive as it is now.