I would love to sell my items with cheaper post but I must add $2-80 onto every item. I can fully understand why some sellers charge more for postage, while others run the risk of not being covered if a buyer chargesback.

Umm...no you don't, if the item is valued at OVER $50 you'd send it that, otherwise you'd just make a claim at Aus Post for a lost parcel (who give you back up to $50).