It isn’t uncommon to find mobile app developers that are frustrated at the low amount of revenue they received on their apps. App development can require a significant investment, and earning back that investment can be a challenge. Many developers have versions of their apps that are ad-supported, but making money from advertising can be hit or miss. For every success story, there are hundreds of people struggling to break even. It doesn’t help that there aren’t very many advertising dollars set aside by advertisers for mobile apps.
Don’t worry too much developers. There is a light at the end of the tunnel.