The 100 Mbps up and down mentioned is USD 85 per month at the current R 14.45 to the dollar in Johannesburg itself.
However, outside the urban areas internet is slower and there is not fibre yet. Cellphone coverage is generally good. For some "inexplicable" reason, however, 1GB cellphone data has been stuck at R 149 for over 5 years now...
You can get cellphone data for much, much cheaper (try Afrihost mobile).
Having recently moved to US, I'm amazed at how backward fixed internet access is here and how first-class it is in SA. Fibre is rare even in urban areas, I specifically asked my estate agent to find someplace with Comcast competition at best and Comcast fibre at worst - she couldn't manage either.
On the fibre topic: That's interesting, I know the regulations are backward thinking in relation to the EU, but I would have thought fibre would be more widespread.
How have you found the move, work wise? My impression in JHB is that core economic activity is suffering (e.g., contruction) but people with mathsy or programming qualifications get jobs easily. Case in point: I have a Mathematics MSc and can get a job very easily; however, a Biology MSc looking for an environmental job simply does not. Any area that requires govt input of course will be less focused on quality and integrity of work.
The issue with SEA is almost entirely to do with shitty telcos who run barely adequate gear, are staffed with semi-competent monkeys and who have no participation in peering fabrics. Yes, the infrastructure is in rough shape as well, just like in Africa.
The latency down here is a killer, often 300ms+ to EU/US, and for chatty web apps, a real pain.