Your account will be charged for each request.
The cost can be calculated on the Pricing page.
Google Play App Competitors Live
This endpoint will provide you with a list of mobile applications that intersect with the target app for its ranking keywords on Google Play. You will obtain the IDs of competitor apps along with search volume and ranking data on competitor ranking keywords.
The returned results are specific to the app_id specified in a POST request. 
The app_id parameter can be found on the Google Play website as a part of a URL pointing to a specific mobile application. For example, here is the URL of the Telegram app on Google Play:
https://play.google.com/store/apps/details?id=org.telegram.messenger
The app_id of this app is org.telegram.messenger