Scoot is offering 20% off their Gold Coast airfares. $300 return isn't the cheapest ever but fairly close. Bags are an extra $35 each way and bags + food $49 each way.
Find the cheap dates in Google Flights then plug them into Scoot's site. I found the cheapest to be July but the promotion says fly by Nov. 15.
- Travel Period: From 10 Sep 2018 - 15 Mar 2019
Also on sale based on this hilariously topical FB post, Scoot are offering fares from $219 one way which works out to $456 Return. Again, Google Flights can help you find the cheap dates. The cheapest dates I found were from November, December. Not the cheapest ever but reasonably good. Bags are an extra $62 each way or bags + meals $112 each way.
Berlin is $545ish but covered in this deal.