Assuming that the thing I read on the internet regarding the Discounted Harville method was correct, and that I didn't stuff up my implementation for 12 runners from the example that was given with 7 runners, a "fair" price for the winning trifecta (given the win odds for the field - and using the presumption that the odds are a somewhat accurate representation of the true probabilities) would be $72,844.14.

As a general rule, I suppose you should avoid betting all combinations that are of greater value than the pool size. (Though that's quite a lax rule as it's likely you would share the pool with other winning bettors).


...just for interest's sake, the fair trifecta price for the three shortest runners would have been $34.37.