Sellers: Buyers HATE excess post.
Hiya, nothing gets my goat more than sellers who overcharge postage. I am a seller and a buyer.
I had a seller who flat refused to send my item in a 3kg post satchel ($9.30) because they only sent in boxes because of damage to plants....fair enough.......except that when I got my plants in a box with $14 post charge the plants in total weighed under 500g, so in fact could have been sent in a 500g post satchel for $5.20 (at the time)!!!!!! ANNOYING.
Or the guy who was charging 14.99 post for an item that weighed 110g.......I queried......he said "Oh part of the cost of the item is included in that". When I pointed out that was a no-no in ebay policy he changed the listing to $1......I bought the item, it cost him 0.55c to send!!!!!
I'm sure you've all got similar tales.
Example of unreasonable post. When a seller charges $10+ post but sends in a $6.60 post satchel.(2011)
If you're going to charge a handling fee STATE IT CLEARLY IN YOUR LISTING.
Same if you send all items registered.
Same if you only use certain types of post. Eg: I only use 500g and 3kg prepaid post satchels because I don't live near a PO.
If it's stated then buyers can have no come-back.
BUT YOU CANNOT INCLUDE PART OF THE COST OF ITEM IN YOUR POSTAGE CHARGE.
As a seller of plants, some buyers items may come to 600g, so I have to use a 3kg satchel. I then pack extra plants to well over a kilo in weight in those instances so the buyers feels they've gotten value for their postage. It goes a long way to acrewing repeat buyers.
Something extra is always good PR, or excess post returned to the buyer via paypal, (gold coins in with the item).
Buyers can request that you send a particular way, that should be no dramas, as long as they pay any excess post required or understand that you take no responsibility to send differently to your listing. All within reason of course.
But by far the simplest way to avoid postage issues is state your options clearly in your listing.