Tickets from LAX to many cities in Australia, from Melbourne to Cairns, are on sale for $660 to $700 for most of 2019 with multiple airlines. Low fare departures start in February and run through end of schedule in November 2019 with American, Qantas, Delta, Virgin Australia and United nonstop flights to several destinations. July is the month with the least low fare dates, but still some availability in the latter part of the month.
San Francisco to Australia is about $70 more round trip.
Qantas Airlines Los Angeles LAX – Brisbane BNE – Los Angeles LA nonstop flights
United Airlines Los Angeles LAX – Sydney SYD – LAX nonstop flights
Virgin Australia Los Angeles LAX – Brisbane BNE – Cairns CNS – Melbourne MEL (20 hr layover) – LAX