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From http://www.border.gov.au/Trav/Ente/Goin/Arrival
"Currency
There is no limit to the amount of currency you can bring in or out of Australia. However, you must declare amounts of AUD.10,000 or more in Australian currency or foreign equivalent.
You must disclose any promissory notes, travellers' cheques, personal cheques, money orders, postal orders or other bearer negotiable instruments, regardless of value, if requested by one of our officers or a police officer."