The best thing to do if sending via Aus Post is use the calculated postage option after testing the final parcel weight etc - once you have the correct dimensions of the parcel, you can fill in the specs on eBay (height, length, depth and weight), and the postage should be automatically calculated for each individual member (it's based on postcode to postcode, so just make sure you enter yours correctly).

The displayed cost is postage only, so if you want to add any for packaging, you can either put an amount in as a handling charge (this is automatically added into the final P&H cost shown to buyers), or add it in to the item price.