Honestly - nothing worse than a buyer hitting BIN then trying to cancel the transaction. I always assume it is some 12 year old. If you don't want it, don't buy it. If you buy it and change your mind, suck it up and resell it once you get it, if you want. EBay's position is that buying an item is a contract. You are trying to get out of the contract, then further confuse the issue by paying for it.
Really this is a bad buyer issue, not a bad seller issue. No offense.