The other issue with this too is the on track "opening" price is not the true opening price, the true opening price is what the corporates and TAB open their fixed odds betting at. The on track opening prices are usually a consensus of what the market has done since the bookmakers opened.

A prime example here is a bet I had on Sunday at Ararat, in R5 the 2nd placed horse Alternative Choice opened on track at $4.60 and the SP was $4.00, I took $13 win and $3.75 place on this horse the day before when prices first came up thanks to a massive error from one of the corporates. The average opening price of the 3 corporates that put up the early prices was about $9 which is a long way from $4.60 on track opening price.