cost

I am new to this stock.
Reserve and the grade are yes excellent, but whether the production cost is high?

i noticed that most of the ZINC-LEAD reserve is underground 300-500m.

So at grade 10%, ore/t valued at $255 at current price.
But how much need to pay to dig out 1 tonne ore from 400m underground? I think may be cost $50/t. then how much need to pay for the processing?

Any ideas?

Thanks.