Vodafone got the 320GB SIM (normally $320) for $199 at Officeworks right now. It’s a 12-month prepaid SIM, you’ll get 320GB on your first recharge, then 220GB after if you stick with it. A 100GB bonus up front.
Personally I don’t go through more than a few GBs a month, so this is way more than enough. Works out to about $16.53 a month for just under 27GB per month on average.
Vodafone themselves are running the same deal too, so up to you where you grab it.