[PaulHoule]

You can definitely win money at the thoroughbred or harness racing track, not by picking "the best horse", but by waiting for a bet that is terrifically mispriced. Maybe once a day there is one that is so clear to me that I can do the math in my head, otherwise it's a game of running my model on my calculator, applying Kelly to decide bets, etc.

The "dollars get left on the floor" because the opportunity is limited there. At my local track I'd estimate that a bet more than about $50 would move the odds into a bad place for me. If I have a big bankroll I can't make Kelly bets anymore and my rate of return goes down. People who are good at this and serious about making money start their own sports books, trade derivatives, or something.