Thanks to this thread, I picked up 2 SIN-DOHx-OSL-DOH-MEL for just under AUD2.5k each in J.
Side note:
For a single passenger with the VISA code, the price was around AUD2.6k IIRC.
Also can go even cheaper by doing open jaw SIN-DOHx-OSL, HEL-DOHx-MEL for around AUD2.3k IIRC.