Every account gets 100 Free API calls per day. If your app needs more API calls per day, you can load your wallet to buy any number of API calls. To buy credits, visit this page and click on "Add credits "
Each model requires different computing resources. Pricing for each model can be found under the "Pricing" tab on each model page. The tab contains an easy-to-use cost calculator based on your standard parameters.
If you are a large app with over 1 Million requests per week, you can use the service by adding your credit card to run your subscription. This will help avoid billing-related disruptions in your API usage.