Airbnb and Booking.com show you a price in AUD. You fully expect to be billed in AUD, from an Australian entity.
The company bills you in AUD but from a billing entity overseas. This might be like the situation where you choose in which currency to be billed, I'm not sure on the exact mechanics. But close enough.
Crucially, you are not informed that you are being billed from an overseas entity. No indication whatsoever.
Your bank, seeing a charge from an overseas entity, applies their surcharges. Whatever they are.
And so you pay the amount you expected to pay - totally cool - plus some surprise surcharge - totally uncool.
If the billing location is relevant for the fees, one would assume that consumer protection legislation requires to display the billing location before the transaction is approved. Whether all foreign businesses will follow the rules is another story. But if no such rule even exists that seems to be a gap in Australian consumer laws. (And as a sibling comment indicates in the US. But the US is generally more business-friendly than consumer-friendly, so I am not surprised.)
The company bills you in AUD but from a billing entity overseas. This might be like the situation where you choose in which currency to be billed, I'm not sure on the exact mechanics. But close enough.
Crucially, you are not informed that you are being billed from an overseas entity. No indication whatsoever.
Your bank, seeing a charge from an overseas entity, applies their surcharges. Whatever they are.
And so you pay the amount you expected to pay - totally cool - plus some surprise surcharge - totally uncool.