Price discovery in action!
I don't accept your offer today (and will treat it as non-binding going forward).
However, we now have a more tightly defined range for a market value of a 5 BTC MS-65 graded specimen: Somewhere between 10 and 18 BTC.

As time passes, if no-one takes the buyout, I will lower it.
Others are welcome to improve upon this offer of 10 BTC.

Thanks for getting the ball rolling, lucky7slick.