Kerri,   there was actually a recent post following a problem i had with under paid postage.    One of my buyers had to pay a small parcel rate of 6.60 to pick up her package (which i had sent as large letter )   my return address was on the package but auspost did not let me know.  Another seller had the same issue.  So apparently now auspost is targeting the buyer with underpaid postage.  My buyer was very understanding and i immediately refunded her that 6.60,  but other buyers may not be and leave negative feedback.     

Also apparently ebay favours free post and puts you closer to the top on searches??? If I understand correctly?