I have sold to Canada, Europe, Hawaii, South America and even South Africa! I have only had one buyer refuse to pay any additional charges on top of the basic fees and so far, and, thankfully, every transaction has been flawless.
That being said, I live in the U.S. and this is a U.S. based site, so I feel no automatic obligation to make stipulations in my ad whether my pricing TYD applies internationally...the one person I had refuse to pay extra complained "but your ad said TYD and didn't mention overseas" and my reply in kinder words was "quit being a dreamer". Anyway, as the seller, I reserve the right to ship where I please,
However, it sounds like you've been dicked around by a few folks with poor communication skills. Sorry you've had to deal with that. I will say it can be just as frustrating for sellers, people change their mind about buying, or are bad about communication. It is what it is. I will say this, me personally, I will not accept standard paypal for an international sale, my policy is once it leaves our shores and customs has to deal with it in another country it's not my responsibility, there just isn't enough recourse for a seller when shipping internationally if something goes wrong. I always warn my prospective buyers about that and I have never had a problem knock on wood.
My best advice is keep trying.