Here is how much a regular package goes from China post:http://zf.chinapost.com.cn/index.do;jsessionid=vZNFR5JGVwVjXKjkSLLtsjjnxY23nrnhS04pz6w0psGq11Tmy41z
If I sent my phi-2 20X4 kit (5 oz) from China to USA/rest of world, I spend around $6, half of what I pay if I send it from USA to China/rest of world. So before USPS price hike they were in par. This is what a typical person pays. As far as I know, China post is also doing very poorly, due to internet (no one is writing letters anymore), and lots of private local and regional deliver services, even private international ones, through which most these free shipping packages go. You will find an NY or CA address on the package cause the package was shipped to NY or CA distribution centers and then cheaply shipped to you via USPS (commercial rate, not our rate).
You also can't exclude some sellers trying to make themselves good names by charging too little.
OK, I really wonder how they get these small packages of parts to the USA for $4-$5 then. I'm only too willing to buy them. Never had any problem with resistors, capacitors, LEDs, voltage regulators, EPM240s, MAX7219s, etc. or the other bits and pieces I have received from China and Taiwan.