Your account will be charged for setting a task and the number of results you will get in the items array. The cost can be calculated on the Pricing page.
Setting Google App Searches Tasks
This endpoint will provide you with a list of apps ranking on Google Play for the specified keyword. The returned results are specific to the indicated keyword, as well as the language and location parameters.
Your account will be charged for every 30 results returned, e.g., if you specify "depth": 31, you will be charged as per 60 results.