If you race off to Sportodds website,you will find,what Floydyboy calls roll-your-own odds.
If you analyse these you will come up with a formula or graph of converting margins to prices.

I use a formula to do same.
It is K^M+1

where K=0.955
and M= margin

So for example
if you think Essendon can beat Brisbane by 12 points

First do the power part
0.955 to the power of 12 equals 0.575
Then add plus 1 equals 1.575
Rounding off gives an acceptable price of $1.58
Prediction of a draw becomes $2
A 1 point margin becomes $1.95 for the favourite and $2.05 for the underdog.

Cheers Mo.