The first person to get half of the max profit (currently 5.26BTC) wins a numbered Design 1 /w Gold coin. (18.494302%)
Does this require a payout or a profit of that value?
The natural interpretation would seem to be that you need to
profit by half of the maximum profit.
That would require a payout multiplier of at least 6.26x, which has a chance of happening of less than 16% (else the game would be +EV).
Oh yes, you are correct dooglus. I messed up the calculations, my bad. I've updated the OP.