The points made by others are very relevant regarding other airlines carrying two Captains and two F/O's. British Airways, all the European, Middle East and Asian airlines do.
Have a look at what the long haul Captain's and F/O's of other airlines based in Australia make, and then compare that to your own S/O's, and you'll see why the company is taking this path.
At the end of the day, the law of supply and demand will rule. If there are enough pilots willing to work for the given conditions, then those conditions will stand.