[02/05/2019 @ 9:10 AM] United drops price to $458 with stops.
Qantas and United have round-trip flights from Dallas (DFW/DAL) to Sydney or Melbourne (SYD/MEL) for $458-$553. Flights from February to November. Australian ETA (a Visa) required. Blackout July.
Note: Flights to Sydney are Nonstop or with a connection.
Note: Keep in mind the time/date/season change when traveling.