I can't say what the costs are going to be in Botswana, nor am I familiar with those related to Copper or Copper/Silver deposits.
I used costs from a gold project I looked at in Canada a number of years ago, so the ones I've used should be in the ballpark depending on how far they would need to truck the ore etc.
As for processing the ore, maybe others have that sort of knowledge and will post it?
I know South American deposit's can be viable with a Copper grade of 0.25% when you add in credits for the by-products.
That fact the deposit has been covered in calcrete, seems to mean its not been oxidesed as might otherwise have been the case. I believe that lowers the extraction costs, but have no idea how significantly.