I realise the above values are just example values, I just wanted to point out that using the Goldman Sachs report previously posted, average production costs in South Africa were listed at 280 Rand compared to the 350 used above. Also, freight is listed as ~145 Rand compared to the 200 used. What's even more interesting is the Rand has depreciated ~15% from the time the report was published up to now, as Sun mentioned.
Just some thoughts.