The device cost for Apple iPad Mini 2 month-to-month from Optus are now:
32GB - $384 (Space Grey)
64GB - $480 (Space Gray / Silver)
Please factor in 1 month plan cost, min. $5 My Mobile Broadband Plan (e.g. $389 for first month).
I would assume both device is Wi-Fi + Cellular due to tablet sim plans.
Currently Apple Store sells Apple iPad mini Retina 32GB Cellular for $589.
The Good Guys - 16GB Cellular - $529
Previous post of last offer (expired)