The development of the typical app cost $35,000 and the median paid app earns $682 dollars per year after Apple took its cut. You see where this is going.. We get to break even on our App Development costs in... 51 years. I'd say the iPhone battery will need replacing before then, and perhaps our grand kids have grown tired with that oldfashioned antique toy by then. But maybe - just maybe - without any updates to our app, we can sustain 51 years of continuous sales and recover our initial investment. Yeah, and this is obviously without covering any of our marketing costs, and gives us no profit yet, etc...
Just to break even.
If you take that absolute lowest end of the two estimates, $15,000 and do our app 'dirt cheap' - even then, it will take 22 years to recover our costs.