as said, you get charged for pics, and other stuff while selling. also VAT, also if you accept paypal payments, you are also charged a percentage of what goes into your paypal account, Not the buyer. the little charges can mount up at end of the month if not watched.
so my advice, and i now the the rest of the world looking on wil see this, is to add an extra pound or so to your postage costs, because if its an item that only worth a pound or two, you could actualy end up loosing out in the long run.
sean