Those are some great calculations Argoz!

If I remember correctly, the plan was for a proposed 1500 tpd mill expandable to 5000 tpd with a total production output of approximately 4 million oz silver equivalent per year when operating at 1500 tpd. So those numbers are in line with your estimate of 3.18 million oz per year. The estimated cost was in the $100 million range for the 1500 tpd mill with another $50 million required for an expansion to 5000 tpd. These numbers make the 500 tpd mill purchase from Hecla seem like a steal.

I'm thinking the plan would be to get the 1500 tpd operation optimized before expanding up to 5000 tpd where economies of scale would significantly reduce the operating costs.

How we pay for all this is the real wild card, although I would suspect ECU has several options available to them.