This may be targeted to regional customers (though I can't see how they can tell unless it comes up when you enter your address).
Buy a mobile phone and get the 500Gb plan (stay on it for 90 days) and get 120,000 Flybuys points (worth $600). Some 5G phones get double data.
Some phones are discounted IF you stay on the plan the whole phone contract length (but these ones don't have the double data).
NOTE -
There are 5 offers mixed up in this:
Double data for buying some 5G phones.
Regional Offer - discount on some plans (ends 30 June).
Standard & Bonanza Flybuys points offer (ends 2 Aug).
Discount on phone cost for staying on plan full term.
Looks like you only have to be on the plan for 90 days to get the points, but if you cancel the plan you then have to pay off the Remainder of the phone in full. Quite a few phones of varying types and cost.
Other lower data plans available for less points. Also sim only plans. With 1000Gb you could dump your home internet (though people have been warning 4G speeds have dropped in their areas since Covid).
Or buy a 4G phone and get 500Gb, the Flybuys. Cheapest is the 4G Oppo Reno Z for $30 over 12 months (24 & 36 available too). So that's $1188 over the year for the phone and plan = $99 per month. Or $117 (after you factor in the $600 Flybuys) if you dump the phone plan after 90 days!
Or with the Apple iPhone Pro Max 512Gb (most expensive phone) it's $208.20 for 12 months (2498.40). Cost after 90 days of the plan, minus the points is $2255.40 (RRP is $2499). Thats the 4G plan though (best deal comes with a 5G phone).
Page doesn't work in Safari. Use Chrome (on a Mac).
For maximum benefits:
Click the main link at the top of this page, then click Mobile Phones tab on the Optus page that opens, then move sideways in the selection of phones using the arrow to get to a 5G phone, under the phone payment cost click 'Select device and proceed', then it should show the doubled data in the offer details.
Edited 7 July to remove gift card parts (as its ended).
Depending on how many in your household and what's their browsing habit, I'd say 500gb is still a risky proposition. And still very expensive exercise because after 3 months you're only $240 ahead, if you own an Android you will know that a flagship model will drop more than that during the same period.