RE: Helca mining According to yahoo finance, Hecla's trailing PE is 74:1. In other words, they are barely profitable. Therefore, it costs them close to $27/oz to find, extract, and mill silver ore. Not sure where you got 'under $10 per ounce total cost'. That is probably one of those 'cash costs' numbers mining companies throw around, that don't mean much.
Another way to look at it is that when silver ran up over $5/oz in 2003, Hecla ran up in price to $5/share. Since then, silver has increased to $27/oz, and Hecla is back below $5/share, down to $3.70/share.