If the seller is registered in another country and has a foreign bank, typically in Asia, your credit card or bank may be assessing a foreign transaction fee to cover the cost of additional paperwork, even if there is no actual currency conversion involved. It is not an eBay fee at all, and eBay does not receive the money, your credit card or bank charges that fee to you directly to cover the costs of the transaction.
Check the seller's profile or feedback page to see where the seller's eBay account is registered -- that might be an indication of a seller with a foreign bank account. Sometimes even if an item ships from a US warehouse (or is listed as shipping from the US), the transaction can still be subject to such a fee.
Since the fee is determined by your bank or credit card terms, using a different payment source might avoid such fees. My credit card charges me 2% foreign transaction fees, but if I pay those sellers using eBay Bucks instead, I am not charged a fee at all (so far).
Since eBay has no idea what credit card you may choose to use or the terms it might have, eBay cannot know in advance how much the fee might be -- though eBay could certainly do a better job of making it easy for users to identify which sellers are registered overseas and might therefore cause buyers to incur such fees.
