https://www.airfarewatchdog.com/blog/44256574/australia-on-hawaii-roundtrip-from-mainland-usa/?source=66080There is a fare war between American/Qantas and Delta/Virgin Australia on flights to Australia. Fly from each other's hubs to Australia starting at $810 roundtrip. If you're in Hawaii, Jetstar has flights as low as $429 roundtrip.
ETA (so that you don't click on that add filled link):
Travel from the mainland to Australia is valid on Mondays, Tuesdays, Wednesdays, and Thursdays, departing through November. You may return from Australia through the end of the booking schedule in June 2019, excluding peak holidays.
A sample of fares include:
Honolulu to Sydney $429 roundtrip, nonstop
Los Angeles to Melbourne $810 roundtrip, nonstop
Los Angeles to Brisbane $821 roundtrip, nonstop
Los Angeles to Sydney $822 roundtrip, nonstop
Philadelphia to Melbourne $829 roundtrip
Atlanta to Melbourne $834 roundtrip
Salt Lake City to Melbourne $834 roundtrip
Seattle to Melbourne $834 roundtrip
Atlanta to Sydney $837 roundtrip
Phoenix to Sydney $837 roundtrip
Portland to Sydney $837 roundtrip
Seattle to Sydney $837 roundtrip
Detroit to Sydney $839 roundtrip
Minneapolis to Sydney $839 roundtrip
Portland to Brisbane $839 roundtrip
Seattle to Brisbane $839 roundtrip
Charlotte to Sydney $840 roundtrip
Phoenix to Brisbane $842 roundtrip
Miami to Sydney $842 roundtrip
Philadelphia to Brisbane $846 roundtrip
Miami to Brisbane $846 roundtrip
Charlotte to Melbourne $847 roundtrip
Minneapolis to Cairns $922 roundtrip
Salt Lake City to Gold Coast $957 roundtrip
Atlanta to Perth $1,014 roundtrip