Etihad seem to be having very cheap one-way flights from Sydney to a whole bunch of European destinations at the moment (around $450), including Athens, Istanbul, Moscow, Milan, Rome, Barcelona, Madrid, Paris, Vienna Copenhagen, Prague, Amsterdam and Warsaw. Availability on many dates throughout October and November 2025. Check on Google Flights for availability dates for your destination. Not sure if it's a pricing error, but I've checked the price shows up the same on Etihad's website as Google Flights.
Need to pay extra for checked baggage though - I think it was around $50 extra.