Sorry mate your logic is flawed.
Who cares if it's 3bn, production capacity is 2mtpa.
So 200mt reserve will give you an approx 20 year mine life inclusive of extration and mining loss.
You can value it on an in-situ basis as explore but once a resource is proven project npv is the only valid valuation tool. At 2.8b capes and 2ntpa 5-10 can be achieved all depends on how the project is financed.