Google lets developers create promo codes for Play Store
Google gives app developers the ability to create promotional codes so they can make their paid apps and in-app purchases available to users for free. The codes can be managed in the developer console.
Google’s documentation shows that developers can create up to 500 codes per quarter for an app or an in-app product. For example, promotional codes can be used for giveaways, or to make apps and in-app purchases available to reviewers. The addition of promo codes was noticed by AndroidPolice. Apple has been providing iOS developers with similar capabilities for years.
App developers can specify an expiration date for the code in the developer console, but promo codes are valid for up to one year. If the unique codes are not used, they will expire. It is not possible to reactivate the codes. Also, in the developer console, app makers get the option to pause a promotion. Previously provided codes cannot be activated while the campaign is paused.