If you are using the satchels, the flat rate of $5.50 for the 500gm and $9.35 for the 3kg applies. If you want the satchels to be signed for on delivery and cover to $100 value, it costs just $1 more.

If you are using your own boxes, you have the flat postage rate ($5 for under 250gm, $6.35 for up to 500gms) and just add the click and send charge of $1.50 to that.

Once over 500gms, use the postage calculator on the Aus post site and add the $1.50 charge.

If you want to cover the value to $100, I'd recommend sending by registered post instead as it can be cheaper ( buying bulk registration labels they work out at $2.60 instead of  $3.05)

🙂