Any time you land in a continent, even if it is only a transit, it counts to the continents used. There are some rules that allow you to transit a continent and enter again for a visit later (eg, SWP-xASIA-EURO-NA-ASIA-SWP).

There is currently no way to get across the Atlantic to/from Africa on OneWorld without connecting through Europe. Thus most OW RTW ticket involving Africa will be a xONE5 or xONE6 (due to needing to connect in Europe) until such time as AA or LA start service to Africa or MH joins and retains their EZE flight. The only way to get it down to an LONE4 out of Africa would be to drop either Asia or SWP.

LONE4 (South Africa departure) 21800ZAR ++
LONE5 (South Africa departure) 25000ZAR ++

LONE4 (Germany departure) 28130ZAR ++

I would suggest finding a cheap flight to somewhere in Europe (say MAD or FRA) and starting the LONE4 from there while making use of a travel agent in Canada to pay the cheaper South African price.