If you don't mind hopping around SIM cards (2 hours of your time every time you port numbers), this is the cheapest offer I found around the Christmas/NYE period.
You only need to activate it by 31/03/2025, so if you have another intro offer you like for a different telco, you can combine/chain them.
As it stands of today (2025/01/03), the next best offer is with Felix Mobile ($12.50/Month for 25GB, First 3 Months, 1.5mbps data excess so effectively unlimited).
Happy deal hunting!
Why is everything so damned expensive?
Ported to telstra $2 sim on new years eve and port completed in 5 min