If you don't learn this stuff, you're going to lose more than a good grade. It's not just the dollars that motivate, though. The process of competition does so much for the class atmosphere. Material that could have been horribly boring becomes really lively. Kolberg doesn't base students' grades on their rank or dollar amount, because the best students aren't necessarily the highest in rank.
Students have to show how they arrived at their decisions, and they have to take tests.