True, somehow sellers in China can get by selling items to the US for less than a buck on eBay, shipping included. I never understood how this worked. Just mailing the same little item within the US would be like 2 bucks, plus eBay fees.
The postage thing was explained a while ago somewhere, possibly HN: there's no "settlement" between international postage services in the normal sense, and there's a HK postal service that will ship to the US for pennies. Once it arrives in the US postal service, it's their cost to deliver it.