I have tried to use the workaround of setting up the supplier in USD and using an exchange rate.

But this does not apear to work because the primary issue is, QBO thinks the USD amount is AUD, and you can never change this amount, i.e. the exchange rate will only change the USD Amount and not the AUD amount.

So whilst the issue is that QBO is pulling the USD amount into QBO, QBO thinks it is an AUD amount.

There apears to be an issue with script QBO uses when pulling these amounts in from Paypal.