I made some enquiries the other day about US to Australia sea shipping (for future reference). I was told by 2 freight forwarders/agents that all the clearance costs once it has arrived here will cost $700 -850 approx. (as wotto estimated in the previous post)
So if you get an agent to do everything, their is the US senders shipping charge, plus $700 -850 to clear it here, plus taxes if it exceeds $1,000.
Also DHL don't do US to Australia "one off" private sea shipping deliveries, only business.