As mentioned above I don't see how halving fares is going to get a lot more people travelling.
Family of 4 MEL - OOL, airfares 400 ish
Accommodation for 5 nights 1500 to 2500
Hire car 6 days 4 to 700
Food and incidentals 1000
Alcohol (because your travelling with 2 kids) 1000
Airfares are, and have been for some time, the cheapest component of a holiday in Oz