I'm not in Australia but I've never found it cheaper anywhere else brand new. However, if you're looking for a deal, check out refurbs. You can shave a hundred or two off of the purchase price, and retain the same warranty and get an excellent product. Apple refurbs are generally very very good.
I got a 27" Apple Cinema Display through Amazon.com for $799 refurbished, that's about 20% less than new retail. ACD and Thunderbolt Display are the same price, though I went with the ACD so it would still work with my non-thunderbolt machines!