This deal (which looks pretty common) is back. The Boost 140GB SIM deals for ~$150 are probably better value (depending on network preferences), especially with international calls/texts included, but Boost doesn't currently have roaming at all. Optus seems to have one of the better prepaid roaming offers which may be useful to some.
Includes 20GB bonus data for new customers. Purchase by 19/09/22 and activate by 26/09/22 on the Optus Flex plan.
Optus also does eSIM - which Boost doesn't yet.