Hi Koekrooster.
I started to keep track of the costs, but quite quickly realised that it would cost me a lot more if I did not do the trip. I would always regret it and you can't put a price to that.
To answer your question, I would estimate around R20 000.00 to R35 000.00, depending on what you ride, how far you ride in total, where you stay, what you eat and what attractions you want to pay to see. The amount of border crossings and subsequent permits and insurances, that will be required, also contribute. I did 12000km in 5 weeks through 4 countries and I estimate my total cost to be around R35000.00.
But, it is worth every single cent and more. I am definitely doing it again, different route, next year.