Hi There... what I have done in the past is do the calculations myself and put the cash difference in with the parcel as a refund. Then, because I posted the combined items ...'Tracked' I might add! ...plus the items were delivered ...and the buyer left a glowing Review... Ebay punished me by making me wait 2 weeks for the payment because I didn't use their service. Even though the proof of item delivery was there in plain sight. Ludicrous!! You respect the customer, give them what they want ...are out of pocket yourself by doing the customer a favour ...then you get reprimanded by Ebay ....'Because They Can'!!! Clearly Ebay lose out massively on postage commission when seller take it into their own hands to do it independently.