Personally, prepaid data is what I would really love. I am often back in Australia for one month every one to two years, and an iPhone without data is such a useless device. A beautiful, shiny black mini computer in which all the useful functions aren't available. So frustrating.
Neither of the major players here, Telstra or Optus, seem to do prepaid data, although they're in the same ballpark for postpaid: https://www.optusbusiness.com.au/shop/mobilephones/packs/mob...