My 2 cents worth in laymans language, Crash what you say is CORRECT, however, (as Chrome says, the odds are remarkably accurate and close to break even in most cases when commisions are added back) we are talking about many 1000's of races so that 10-1 is calculated INCLUDING the 1 race in 500 when the jockey falls off etc. in the same way as the odds are slighly better (on a sliding scale) the better the draw etc. Overall the book seems to be pretty accurate the lower the price and slightly worse (on a sliding scale) the higher the odds but overall it comes back to the book being set at 118 or whatever, does that make sense?