I believe the parent is actually saying that the financial incentive is used to select people who know what they are talking about. It's not necessarily a 1:1

I believe the parent is actually saying that the financial incentive is used to select people who know what they are talking about. It's not necessarily a 1:1 match, but basically that selects for people who believe that they know what they are talking about (and thus are less likely to be swayed by the group opinion). To the extent that the current price of a proposition in prediction markets represents the group opinion, you only expect to win the bet if you think you know better than the group opinion.