I dont think your numbers include the JV contract terms, exchange rate, project improvements the JV has been working on the last 6 years.

Project improvements means alot of things, but its clear that the SC project has changed immensely since December, 2012. Have you been following the company? Not even including the conversion- the generating ore revenue from the inferred resources currently as a waste cost, you should include exploration potential as a factor to a higher buyout price. Most majors use this metric to justify some price premiums.