Hi, SA dev here (Cape Town). A starting salary is usually 18-22k, a mid-level position is usually starting at between 30k and 40k and for experienced devs (around 5+ years experience usually) around 50k and I'm sure lots of people get more.

As for costs of living, 50k is a really good salary. See the "developer big mac index" here: SA ranks number 2 https://stackoverflow.com/research/developer-survey-2015)

Milage varies if you have dependents to support though - private school especially gets expensive if you choose go that route for kids.