Nice coins. I struggle with your valuations.
And the "tenth" coin is going for 15x face value? I guess I see your rationale for the higher valuation, because only 800 where minted, but 15x is way too much.
I can answer that one...
Firstly, mintage of the Bitcoin tenth is low as you've already said.
Those that have gotten their coins graded haven't received high grades and an MS-66 is considered high for this specific coin.
Most average MS-64/65. Because there aren't many of them with this grade I guess it's more of a seller's market wither regards to determining the price.