The interest rates on American Express credit cards in Australia can vary based on the specific card product and the applicant's creditworthiness. Typically, American Express credit cards offer different interest rates for purchases, cash advances, and balance transfers. As of the latest information, the purchase interest rates can range from around 12.99 percent to 20.99 percent per annum, while cash advance rates may be higher, often around 21.99 percent per annum. It is important for potential cardholders to review the specific terms and conditions associated with each card, as factors such as introductory offers or promotional rates might also come into play. For the most accurate and up-to-date information regarding interest rates, individuals should refer to the American Express website or check the specific card terms.