You're pricing the error coin at 6x face value?!? You realize that it's the most second common coin issued by Mike, right? Over 5,000 of these error coins remain funded (of a 6,000 mintage).
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 look forward to seeing what these coins go for. My opinion is only my own but I believe the rationale on some of the offer prices for these coins are just insane and, worse, without logic. I think it's an important discussion for us all to have.
Cant speak for the error coin but if you find a casas tenth below 1 BTC please let me know. Would buy em at that price point all day. 1.55 btc is not too far fetch. They have been selling in and around there for awhile now.
Why should the tenth be 15 times more expensive than other coins with similar mintage? Just because people want that much doesn't mean people should be paying it. I bought my tenth for BTC0.71.
If we want fair prices we have to agree to only give fair bids and only accept fair offers.
You do not multiply the markup times the face value. There is a 1BTC + premium for these coins. All Casascius silver coins command at a minimum of 1BTC+ of a premium. Take a look through previous sales and you will see the pricing trends.