For most countries, using cheaper calling cards, they usually cost between 1 cent and 3 cents per minute, though to call some countries it could be as much as 25 cents per minute. Some cards are ridiculously high - over $1 per minute, but you can find cheaper deals.
If you are calling from a home phone (not a cell phone) then International calling cards can be less expensive. You can easily shop around and find a much better rate than what your phone provider is charging.
Sprint does not offer calling cards, but they do have a plan available for one to use to call internationally. The plan only costs $15 per month for one to call over 140 countries.
The cost of calling China from your location can vary depending on your phone plan and service provider. It is recommended to check with your provider for specific rates and any potential international calling fees.
The main reason anyone would use an international calling card is the enormous savings you can enjoy when phoning internationally (as much as 76%). Additionally there is the convenience of the card itself, no worries about unexpected bills or charges and mobility and flexibility.
how much does it cost
That depends on your telephone carrier and your calling plan.
It depends on what kind of cards they are.
$2.20 on some websites and no shipping cost
£1.00
$10
It depends where you buy it from.
You don't need another SIM card. If you want to use your phone in another country - simply contact your service provider and ask them to activate its 'roaming' function. Be aware though - that calls will be much more than if you were using your handset at home !