Wind and Solar Power Facts, page-23

The cost of the renewable energy in SA is lower than the cost of the fossil fuel power that supplements it.
That's why the cost is higher than usual.

I know you all like to believe that coal and gas are cheap but in this case they are often very expensive.

Of course you can supplement PV solar with thermal solar and with wind and with hydro and with wave and with tide and with geothermal and meld them all together with some batteries including molten salt for the solar thermal.