I (on my other ID) experienced a similar scenario last year with a US buyer who bought $800 of goods from me and about  $10,000 worth of goods from 10 other sellers, all non-US. Items were shipped to a US post box and the buyer claimed item not received against all his sellers.

There were three holds on my funds

1) paypal "invesigated" the transaction for a couple of weeks - I supplied my proof of postage and all was well

2) The buyer opened an ebay.com buyer protection case. I'd posted by express courier international which supplied the required online proof of delivery/signature. Paypal put a hold on the money again and released it after a couple of weeks.

3) The buyer did a credit card chargeback. I suspect he won this but paypal covered me with seller protection so they lost money, not me.

I talked to many of the other sellers: many had insufficient postal tracking to satisfy ebay.com seller protection requirements.

They deregistered him from ebay fairly quickly (by ebay standards), about 2 months after he started the INRs.

I notice the OP's buyer is in Germany. This has the potential to make things more difficult if he was logged into ebay.de when he purchased and tries to use ebay Germany buyer protection rather than paypal protection.  I'm not sure of the fine details of the German policy (since it's on the German ebay site in German), but be aware that paypal Australia won't cover you for claims via German ebay. You'd need to satisfy the seller protection conditions specific to ebay Germany.

Hopefully the buyer will stick with the credit card unauthorised use chargeback, which is dealt with by paypal Australia, not ebay.de.