Get someone to drive it for you and they charge you X amount which is cheaper than R 4k. They drive your car to Durban and then fly back to CPT. If I stayed in CPT I would have done it for you for R 1k excluding flight price and fuel. Not to bad for a day's work
Try all of the carrier companies, as trucks normally head back to Durban without any cargo, so it should be cheaper doing CT to Durban rather than the other way round when they are usually full.