Analyzing and monitoring your App, once it has been published in the AppStore, is an important task to make your App a success. If something is crashing in your App on a remote device, there should be a communication mechanism to notify the developer about the crashing event. Also, developer should be able to see the detail error logs of that device.
Generating revenue from the free apps is not like dip and sip, once you developed an app, the next step is to submit it to the app store (Apple/Google Play/Windows). But a question always arises in your mind is "How much should my application price?" and therefore evaluate to keep it either free or paid can be difficult.