Finish Powerball Classic Megapack 110pk @ $14.99 (13.63c each - which is cheaper than ALDI's Logix Platinum 10 in 1 40pk for $4.99, which is $16.63c each)
Overflow is a Queensland discount store, but there are a variety of other Dollars and Sense type stores Australia wide, so this may also be available elsewhere.
In Queensland, they are in the following locations: Jindalee, Upper Mt Gravatt, Cannon Hill, Browns Plains and Morayfield
In case anyone is going to the Cannon Hill store, it is still there, but has moved three stores to the left. I thought it had gone when I couldn't see it in the previous location, but it is now next to the lighting store.
As of 6pm, I saw about 30 boxes of powerball tablets left, you pass them as you go into the store, very close to the cash registers. They aren't exactly the same as mentioned in the post above, 90 per box instead of 110. Still a good deal.