Australia Post, along with many other country's postal services, signed on to the UPU agreement many years ago. Under the agreement, all partipating countries A) retain all of the money they receive for international postage, and B) are obliged to deliver international packages (to a comparable service standard).
That means yes, other countries - particularly export-focussed ones like China - can take advantage and have minimal costs to send international mail, knowing that it will only cost them whatever the domestic portion of postage and putting it on the plane is, while other countries seem to take the opposite tactic, but no one can dictate what another country's postage prices are, and it's not a conspiracy or a special deal, it's - by and large - business.
What does happen, though, is that any country that receives more mail from a particular country than is sent there will be eligible for (and receive) terminal dues for the difference, meaning AP charge you $30 for a service than wouldn't cost them that much more than a domestic parcel, keep all of that $30, and also get paid (annually, I believe) for the difference in volume of mail they deliver from China (they do say this doesn't cover actual costs, but they never say what the actual costs are, nor how much of a gap there is - I know they post loss amounts in connection with this situation, but they don't even clarify what the amounts are based on).
Re: the trademark issues, I can't advise beyond the basic stuff, so not much help there.
