Not a bad day (result)
Melb
Outlay $1 for each runner to win cost $18
Total return =$21.2 Net Profit =$3.2
POT =17%

Sydney
Outlay $1 for each runner to win cost $17
Total return =$7.8 Net Profit =$9.2
POT =-54%

Adel
Outlay $1 for each runner to win cost $15
Total return =$15.4 Net Profit =$0.4
POT =2%

Bris
Outlay $1 for each runner to win cost $18
Total return =$26.5 Net Profit =$8.5
POT =47.2%

All Together
Outlay $1 for each runner to win cost $68
Total return =$70.9 Net Profit =$2.9
POT =4%

It's better than bank interest