i am chinese;in my country;we use second-hand bb nearly;it costs 20;but i want to ask how much it is a new one ;

It depends on the device, the carrier that you use and if you get a 2 year contract or not.

You should be able to use Google to check the major US carriers, AT&T, T-Mobile, Verizon and Sprint.

If you are looking for a US phone to use in China, then you should get one that is sold and supported by your cell carrier.