I can't speak for the US situation that
@Tel is in, but I have done many purchases of stuff overseas where I've had to pay taxes and fees, since that has been SOP around here for years now. Most of the time it's a straightforward process; I just keep in mind how much it's probably going to cost me when all is said and done and that's the price I base my purchase decision on - not the list price of the seller. I think that's where a lot of the disappointment comes from. You see something for sale for $100 and by the time you have it in your hands, it has cost you $150. The first time that happens, it's disappointing. But if you factor in the cost, it's just one extra step in making your decision and the net result isn't too different from purchasing domestically.
The list of stuff I've purchased overseas is too darn long. Maybe a few recent examples:
Some washi paper from Japan. Seller did not offer to levy taxes or do customs declarations, so those are handled by our domestic customs, who generally delegates to the local expediter; I understand this practice is conceptually the same in most countries. Package was not opened, I just received a notification from our postal service (the local expediter) telling me that a package was about to arrive, prompting me to pay the taxes & fees. Did that electronically and the package was delivered. This process used to be more cumbersome, but over the years it has become more streamlined.
An alternative workflow is if the seller offers the possibility to pay taxes and do the customs declaration, in which case the purchase process is virtually the same as when purchasing domestically. I just get to see the total price including all taxes & fees and that's what I pay directly to the seller.
I've also purchased chemistry from abroad that logically triggered suspicions from customs and law enforcement in Europe, so some of it was opened for sampling, then neatly taped shut again and delivered to me with a small delay. Customs inspections are selective (and not random), so sometimes a package takes a little longer as it needs to go through that diversion.
My eBay purchases are rare and most of the time they're from within the EU; on the rare occasions I did order something from a different tax zone, the eBay-associated clearance service worked fine.