API gateway fee is calculated by the number of API calls and outbound traffic. It is free of charge during beta testing.
API call is billed per 10,000 calls/month. Less than 10,000 calls will be billed as 10,000 calls in one billing cycle. The fee amount has a precision of two decimal places.
The rate is 0.6USD/1,000,000 calls.
Outbound traffic fee is calculated in the same way as the CVM outbound traffic. For detailed charges, see here