i think the no changing for teh cheap tickets is a bad move by qantas.
sure i don't fly alot but when i went from SYD-BNE with a group of 7 we turned up 4 hours early.
alot of flighs went out with plenty of room.
along came our evening flight.
It was oversold :-P
if they had let us go earlier it would not have been
now imagine if this happens about 200 times a day with a few seats involved.
it adds up