Optus are currently offering 200GB for $60 on a 12 month contract, or $80 on a month-to-month.
The double data promotion is relatively normal now, but I've never seen data plans be eligible for a 25% discount AND double data for 12 month contract before.
UPDATE: Offer extended until 3 Feb 2019
I am on the same boat. How are you planning to do this? Swap the sim out when running out of data?