San Gold Corporation

At 200,000 oz per year, and $1,200 gold with an all-in cost of $600/oz means the company is spending over $200/t of ore mined, assuming average grades of ~1/3 oz/t. That's way on the high side, even for Canada. In such a situation, however, you are correct in saying the net present value of the future earnings of such an operation projected out to infinity is ~$4/share, with the current share structure, assuming a 5% discount rate. (With reasonable discount rates of ~5%, earnings after 25 years don't contribute much to NPV - picture it like inflation, and you'll understand implicitly why.) You're also assuming no further expansion of the mill, which is highly unlikely in your scenario.

I'm not nearly so skeptical that they won't be able to bring their costs more in line with the rest of the industry at ~$120/t, in which case the company should be worth ~$8/sh.