VN PVG-MEL J (rtn) for RMB7888 (USD1203)
Limited availability, sample dates 23NOV-6OCT and 1NOV-15NOV, but there are plenty of others available. Searching on the VN site seems easiest as it gives the fares each way on a calendar bar at the top of the page.
Return fares including tax RMB7888 (USD1203). Haven't checked if the fare is also available to SYD.
Flights on the A359/787 with full flats. Looks like some combinations require an overnight in SGN on the way back.
Can also book on ctrip for RMB8146.