I am relatively new to Ebay and have had a great experience so far. I have found that the postage calculator has worked really well generally, with the postage being exactly what was estimated with most items sent. But I have had 2 transactions, one which cost me way over my estimate, but I figured it was my fault, learn and move on, but the other was overestimated, the buyer paid $6.95 but the actual charge was $2.80. It was strange (this was a book) as all the other books worked out exactly right. My question is: should I refund the $4? Is this something buyers expect? I have read through a few posts and most people are saying that when you state postage and they still purchase the item, then it's their choice, I guess I feel you shouldn't make money on postage? I would appreciate some of your thoughts. Thanks.