Supercheap is doing a runout on Mobil 1's, according to my local store they're discontinuing them completely hence the prices. If you're lucky and found your local store to have store (that's a struggle…) then they're cheaper than the usual suspects on eBay. If you're unlucky and ended up needing to get them shipped from their warehouse in Gympie then it's a so-so deal. Still slightly cheaper than from eBay.
Note: Stock level are low and availability are hit or miss. Be warned.
EDIT: as if Mobil will stop making this, it's just Supercheap will no longer stock Mobil 1's. Probably Mobil's in general as all the Mobil oil have disappeared off the shelves at my local.
EDIT #2: All the 5L 0W-40 and 5W-30's gone. All the 1L's still here…just. You could ring 'em up and get them to check their stock system to track down where are they still available at as their online stock allocation is somewhat separate from their physical store's stock allocation.
Wow that's cheap.