Hi ..No , you do not have to pay additional. Here is policy and you can forward to the link to seller and refer to terms and conditions within..
http://pages.ebay.ca/help/policies/selling-practices.html
I might consider paying the $3. but i would want the seller to know that this is not acceptable as a practice. If a well established seller i probably would not.
If seller refunds your payment can leave appropriate feedback and DSRs and do not agree to any cancellation of the sale.