Supply and demand at work -- the essence of capitalism. But fares are really quite reasonable, for example today I can book PDX-MEL for USD 1050 while PDX-NRT is USD 928 (a shorter distance and also non-stop flight) and PDX-HKG is USD 1058 (about the same distance).

Seems like pricing is pretty similar. The below-cost pricing that occurs on some Asian routes on some dates don't happen to Australia, but you have to have date, trip duration and destination flexibility to take advantage of those bargains. For normal travel, Australia is priced similarly.