Good catch but it is after you win the price.  Isn't it?  So winning the amount from the prediction, you do not stake anything. Thus, you did not gamble or put a stake that comes from your purse at all.

Withdrawing the winnings is another part where you wager your winning amount.  If we connect it, you still don't wager anything from your purse at all because you did not stake anything in the first place.  You are playing with the host's money, right?  And it will be yours once you meet the requirement.