The 3 g will have a card installed for AT&T I am unsure if the iPad is unlocked
You need to purchase a unlocked iPad then install a prepaid optus, Telstra, Virgin or Vodaphone card. You should be aware that prices in Australia are the same as USA Also be aware that price quoted USA does not include sales tax. What you have to understand is that you have to declare the iPad on entry to Australia which will impact your total duty free amount. my advice is buy in Australia as at the end of the day you will pay the same. It is true the Aus dollar is around $1.8 I would buy other items like clothes etc but that is my opinion.