I have recieved a response from a person at PayPal since I started this thread and I'll quote you some of it:

"Thank you for contacting PayPal.

I can confirm that you have received a payment for $50.00 AUD minus the payment receiving fee of $6.53 AUD.

Transaction fees can range from 1.1% to 2.6% + $0.30 AUD. If you receive a payment from a non Australian PayPal account, you're charged a 1.0% cross border fee.

There is no fee when you pay for a purchase or when you use your PayPal balance to send money or make a payment."