The way the late great Don Scott would do it was...
Divide ones accessed price into say $100 (base figure) for all the targeted selections for the race if they were paying overs.

I have not taken into account the overs of the actual bet placed here.
So , if one gets up , it will pay more than what is shown.

If betting to Price
$4.00/$100 = Bet 25.00
$8.00/$100 = 12.50
$11.00/$100 = 9.09
O/L $46.59
To Ret $100
Prof +$53.41
no matter which one gets up

If betting to odds
3/1 / 100 = Bet 33.33
7/1 / 100 = 14.29
10/1 / 100 = 10.00
O/L $57.62

O/L is usually greater doing it this way.

If 3/1 wins = 75.71 Prof
If 7/1 wins = 56.67
If 10/1 wins = 52.38

Which is not a bad way of doing it especially if one feels the shorter prices will be more dominant on the day.

Cheers.

He had a great run for awhile but maybe he changed his method. It's a pity he died broken [dead broke] by the Bookies!

Thanks Mr Quaddie.

My late mother was no slouch on the punt and died aged 84 with a vast amount of wealth both money wise and in terms of knowledge.

Cheers.
darky.