It might be that the check out page does not reflect the sale price. The price displayed is usually in AUD which are 1.26 to the USD right now. www.xe.com. This would make the actual price in USD about $8.21 before your bank or credit card decides to tack on a foreign exchange. You might want to contact the helpdesk just in case.
10.36 AUD = 8.21003 USD
Australian Dollar ↔ US Dollar
Could be? Unless it's a display thing only on the check out page because it shows only AUD and not the actual price in USD. I've seen this before with other software and everything was fine once the transaction was processed.