Apple Developer Tools
TestFlight is a developer tools app by Apple earning an estimated < $5k/mo on the App Store with 1m installs a month. Below are its 5 current App Store screenshots.
TestFlight generates an estimated < $5k per month in App Store revenue, from around 1m downloads a month. Its listing holds a 4.7-star rating across 788,241 ratings. The app has been on the App Store since 2014. Figures are monthly estimates of worldwide App Store performance.
TestFlight makes it easy to test beta versions of apps and App Clips to provide valuable feedback to developers before they release their apps on the App Store. Developers can invite testers through email or a public link. When you test a beta app or App Clip, Apple collects and sends crash logs, usage information, and any feedback you submit to the developer. The developer may use this information to improve their app and related products. Apple may use crash logs and usage information to improve our products and services. For instructions on installation, testing, and feedback submission and for details on how your data is handled, see testflight.apple.com.
From the App Store listing.