cavortingcheetah makes good points about the ludicrous prices of Cape Town. I recently stayed at The Table Bay and with an 85% discount it cost R1500 (£140) a night.
Other hotels are priced way above European capitals, it's greed and it kicked off, pardon the pun, prior to the football event held last year. The prices have not gone down.
To call Johannesburg a crime ridden slum, unless you are referring just to Hillbrow, is grossly unfair and I must take issue there. It certainly has crime ridden slums but it has some beautfiul suburbs which are safer than many parts of London.