It means that the answer someone provided was perfect. It doesn't have to be a financial question, but if the answer is correct then, if it were a financial decision, it would be the one that lead to the most profit.
It means that you said or did something that was exactly right. When you are 'right on the money', you are not wrong and you have guessed the answer right.
Right on the money is used to describe an instance of someone or something being either absolutely correct about something, or dead on in their aim during some activity.
