I believe you have no option but to pay for it. I'm assuming your package was opened by Quarantine when you got it? If so, in the event you are getting billed for it I believe it's because your package was opened due to the AQIS believing your item was suspicious (e.g- plant matter, mis-declared item etc) and DHL is simply passing on the cost to you. If you package is opened by AQIS due to random selection, they don't charge you for this. If I am correct, the reason why courier companies (DHL, FedEx etc) charge you and AusPost does not is because the way the system is setup. For the courier companies, an AirwayBill is setup and then it needs to be formally cleared etc; which I believe is where the extra cost comes in. With international senders that use the Auspost system (EMS, RoyalMail, USPS etc) it goes through the major mail sorting facilities which have on-site permanent Customs + AQIS setups in which any mail that is opened is re-sealed and put into the system (at no charge). If the package requires Quarantine processing or treating you may need to pay any associated fees.