Let's say my web app has 10k monthly users and it's for free but it runs ads and the estimated earning would be 0.016$ per monthly user which sums up to be 160$ . One part of it goes to Amazon Web Services (60$ ). What would you do with the remaining 100$ ? This estimation is completely inaccurate and abstract. As this is my first business, how can I be sure of my actions? I expect for earning to grow proportionally with the user base. Thanks for any advice :).