MTN's 100MB bundle for R80 would probably be enough for a lot of small users, its a lot easier in practical terms to use an always on connection like 3G/GPRS too where you pay for data rather than time connected.
Virgin Mobile is even cheaper R 50,00 for 100 Meg - No contracts, pay as you go (sometimes a bit slow...) But well worth giving Telkom up, which is part of the problem for Telkom, people are not prepairied to wait for ever for a line to be available, have to put down R 700,00 deposit, then still pay R 100,00 for rental and calls on top of that....
In fact when you add it all up, it's R 50,00 for ISP, R 100,00 for phone rental, and say R 50,00 for call up... so that's R 200,00 for dial-up which will give you 400 Meg with Virgin, and the R 700 Deposit can buy a V360 Cellphone
Fixed line only turns big profits when you have lots of users, Telkom know full well that people are leaving in droves, the damage is done, and it is going to get much worse very quickly