Discovered this accidentally looking for a pre-paid Telstra SIM for our upcoming west QLD road trip over Easter since Optus has some gaps enroute.
Usual $39 / 55GB 28-day prepaid SIM for $13.
15GB + 40GB activation bonus. Supposedly the next three recharges also 55GB. Unclear if these recharges would be $13 or $39 (I only need it until the end of April so I don't care).
Activate by 7 July.
The 6 month casual plan is also on sale at $13 if just having Telstra reception to receive calls is important as opposed to Vodafone or Optus or even a reseller using the wholesale Telstra network.