I don't think the value of an asset is derived purely from scarcity, or the effort required to make it. What if the asset itself has no use?
If I spend 1000 hours making a really bad doesn't, it'll have a value of zero, even though it's unique and a lot of work was put into it.
I haven't created value, I've destroyed it, I.e. All that time and nothing to show for it.