In January 2018 I was able to get OSL-MEL on QR (travelling in November 2018) for £1,450 return. There's no guarantee that there'll be a similar sale this year, of course, and in fact the gate agent at Doha on the return journey (who was aware of the appeal of that route for TP running) told me that I would be very unlikely ever to see such a fare again, but it's a benchmark.
At that fare, choosing QR is pretty much a no-brainer, although in my experience the very good hard product was undermined by robotic and obsequious service.