I've seen US sellers claiming it costs $50 to ship a pony accessory overseas before though. That's definitely not valid. I think some sellers just do it to put off overseas buyers.
It really wouldn't surprise me
You do still get the odd seller here and there that's willing to work with you and ship things overseas (and not charge ridiculous prices for it :p), but sadly they seem to be scarcer than ever.
And that's why I shipped that package to Brazil. (see other topic). It can be done cheaper and secure. I always take the price of the carrier. I also rather buy private to be sure the shipping is not insane.
But today's online world is obviously to get more money on vintage ponies.
Yesterday I went thrifting at my local fleamarket. There is this regular vendor with ponies I have good chatting with. She told me she has no clue what G1 to bring for her table since nobody wants to buy it. Or try to have it way cheaper price. Mostly commons, italians and sometimes a htf pony. So either the visitors are picky on price for something vintage or everyone has them already.