score:9
If you want to transport a substantial amount of heavy stuff cheaply and time is not important, the obvious solution is transport by sea. There are three options that are worth investigating - which one is best/cheapest (or available at all) will depend completely on your specific origin and destination.
Customs is something you'll almost certainly have to deal with for this amount of cargo - either by paying it, or by providing documents that prove it's not a commercial shipment.
As for the delivery time to expect - US East coast to Australia would be a minimum of two weeks, but could easily be a month or more if your shipment has to wait for a container to fill up.