How is it that they have this money in their possession, since they had given it to the girls?

The King and Duke count the money and come up four hundred and fifteen dollars short. To alleviate any suspicion, they add the money they made from the Royal Nonesuch to the pile. Then, to permanently win the town over to their side, they graciously give their share of the money to the three girls, knowing they can steal it back at anytime.