Mackay, not a bad spot, washpool has a seller in Cairns i think, postage is the same from there as well. Is this an Australia Post issue, or Washpool?
Aussie Post. 500g parcel is $8 from anywhere to anywhere within Australia. Add $2 for the bag and you have their $10 P&H fee. Won't matter where it gets mailed from or too, cost is the same.