The only thing that makes sense is 1) it was from Paul Allens hoard (although not restored) and 2) the buyer was wealthy enough to set the valuation with their purchase price.
The old saying that 'something is worth as much as people are willing to pay for it' proves itself once again.
This is reminiscent of the pricing we've seen in art and antiquities over the past decade, which has always been driven by rarity and heavy wallet flexes.
One last-minute thought is it is a tribute purchase made by someone well-off enough to 'tip' Paul Allen (estate) for his philanthropy. <and in the process significantly raised the value of his L1>
In either case, it will be interesting to know how many L1 owners will be contacting auction houses over the next few months.