I'm in Sweden and I've ordered stuff like a single USB cable from China at a price less than USD 1. Still, free shipping, and $1 wouldn't even buy me domestic

I'm in Sweden and I've ordered stuff like a single USB cable from China at a price less than USD 1. Still, free shipping, and $1 wouldn't even buy me domestic letter postage. If the item is small enough, it usually arrive in a padded envelope in my mailbox. Bigger items I may have to pickup at the post office. Most often, it arrives within 2 weeks. I suspect that postal services in different countries have some kind of peering agreement. That they simply assume that the amount of mail would be pretty much the same in both directions and because of that, they don't really charge each other.