Do you mean HK to AU? Or the other way round? I mailed a few times by HongKongPost to Sydney. Service mail takes about 4 weeks to your home. It costs about HK$400 for 20kg (20kg max); but if you mail some 1 or 2 kg, it still costs you HK$100+. The more close to 20kg the better. Haver a look at the HongkongPost website and beware of the box size though. They have very stright limit on the size of the box.