feenix
I agree that the -300 should (your words) be cheaper than the - 200 and hopefully the loads will make it so. But you need the loads to make it cheaper, hence my thoughts of route restructure.
ebt, all I can say is that catching a Virgin 737 from PER to MEL would have to be one of lifes most painful experience. (I guess that is why Q seems to allways be full).
So 2X seating provided by the 190 may be good for the travelling pax, but I can't see how a 100 odd seat aircraft is viable on that route against something like a 767.
BTW I suspect you have not taken into consideration the alternate requirements for SYD - NLK, MEL - NLK or even the best case BNE - NLK.