Should have added to my earlier post...

If you choose to start from another African country then you must of course pay the fare for that country

Base fares for a DONEWC3 from:
Namibia 56,350NAD (price from Sth Africa is 53,640ZAR and 1 NAD = 1 ZAR)
Zimbabwe 7,495USD

and of course you face the issue of purchasing the ticket - presumably from outside the country of origin