What you don't understand is that the Aussie balance of trade surplus with PNG (compared to other countries that trade with us) is largely because Australia is not vacuuming up all our raw resources. Those countries that are pillaging our timber and fish especially are running trade deficits - before you applaud about that as being in PNG's favour, may I suggest that you investigate further and find out that (a) raw resources always give the least amount of revenue/return compared to processed resources and (b) our raw resources are being harvested at completely unsustainable rates. In the end wew'll have nothing because of this resource pillaging and our trade surpluses with those countries (China, Philippines, Malaysia, etc.) will completely collapse, leaving us with nothing.
If you looko at the big picture, you'll see that a superficial look at trade suprluses and deficits with other countries does not paint the true picture of what's happining to PNG and our resources.