I didn't say anything unrealistic now did I?.
Saying they have developed an app for $600 is just Selective Accounting. Somebody who did not consider their own hourly cost, the cost of living, cost of tools needed to do the job and so on.
Probably they calculated only the yearly apple fee, plus what they gave to the graphics designer for a logo and some icons.
In iOS and any other smartphone programming there are two things to consider:
-> The goldrush is over.
There a no nuggets left lying on the open ground waiting to be picked up. Now it is digging and heavy labour
-> You will get exactly what you pay for
A good programmer with experience will know the value and will ask a decent rate. After-all they have to pay for their own living, too.
If
you have the experience of running a software project then you can hire at a low rate. But then it will be your hourly rate as the project manager that counts towards project costs.
Consider what you earn per hour with your current occupation, independent of what you do now. Just take it as a starting point. Then consider the development might take months. Depending on complexity you might need several programmers plus designers plus marketeers plus advertising. Do the math and you will get a more realistic number.
$600 is little to nothing