I wouldnt be surprised if most, if not all, eBay sellers are unaware of this. You see earlier this year I purchased a bunch of plastic cross stitch frames much like the ones in the photo below.
Usually shipping from USA to Canada for something this small and light weight is no more than $9 ABSOLUTE MAXIMUM. I've purchased many on eBay and have paid shipping ranging from $3USD to $9USD depending on how many are being shipped. The ones I purchased a while ago had a ridiculous shipping price so I contacted the seller for a real shipping quote to my postal code. She was kind to pass it for free shipping because she simply wanted to get rid of them and she changed the listing to adjust the shipping to free. Problem is that new international shipping feature eBay has was in place and charged $13USD for shipping. The seller emailed me because she had my actual address from when I asked for a quote but she inquired why had she received an email from eBay telling her to ship the item to KENTUCKY USA instead of MONTREAL CANADA. Together we figured out that the seller only gets the actual $3 or $4 shipping cost and the balance goes to PITNEY BOWES who claims to clear the item so there are no further duties to be paid by the buyer. For all the years I've been on eBay, only once did I have to pay duties on delivery because the seller made an error on their export document by falsely identifying the item. Other than that, no probs. I suspect some American eBay sellers must be wondering why sales are down from foreign buyers. This is why!
$15 to ship three small packs of plastic 2" frames? Ha ha ha oh that is so funny! Craziness!
Most of the craft supplies I use are purchased on eBay and if shipping is insane I skip it. Some sellers are aware of ths and have opted out to keep their sales up. Good move!
Now I pick and choose my purchases more carefully.