Put the costs up and then gouge a bit more.
From the: https://auspost.com.au/business/shipping/satchels-and-packaging/ebay-satchels-and-boxes#tab2
Prices only apply to postage paid through your eBay account. eBay has implemented an online processing fee of 15 cents for Same City and Other Major City Australia Post parcels, to go direct to eBay. This impacts the cost of all parcels purchased on the eBay platform. For the most up-to-date pricing information, please check the eBay platform.
