I beleive the WA TAB pre-post market is quit often ,very close to final winning prices.
They use the form prices from GTX.

One way of converting paper price to possible final winning price , is to multiply the pre-post newspaper price by 0.90 this has shown to have an uncanny accuracy to final div. on many occasions ,if they happen to win.
e.g. $2.00 x 0.90 in the paper = $1.80 this often will be the final price result.
e.g. $3.00 x 0.90 = $2.70

On many occasions where the paper Fav, is showing much bigger prices on the TAB , just before jump , they seen to loose a lot.
e.g. $2.80 in paper $6.00 on TAB at jump time, they seem to fall over a lot

Cheers.

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Cheers.