Your account will be charged only for setting a task. You can get the results of the task within the next 30 days for free.
The cost can be calculated on the Pricing page.
Get Apple App Searches Results by id
This endpoint will provide you with a list of apps ranking on the App Store for the keyword specified in a POST request. You will also receive additional information about each application: its ID, icon, reviews count, rating, price, and other data. The results are specific to the keyword as well as location and language parameters specified in the POST request.