I made an app a year ago. I did it in an afternoon with 0 experience in mobile apps, using Rails + turbolinks ios & Android. It's really crappy but it generates $150/month. Not bad for the time invested.
That's an impressive result, considering the amount of time you put in it. I'm sure this site is filled to the brim with people who created dozens of apps and applications that never made a dime. ;)