updated valuation - silver developer, page-2

I'll try my hand at playing devil's advocate hobo-jo;

The capex costs and cash operating costs are likely to be much higher by the time production starts due to inflation. The estimates I think were done late 2009 and since then the cost of most things has gone up.
Ongoing capital costs will also reduce the profit margins.

On the upside: you forgot to include Interest earnings on cash held into the profit equation; and the silver price is now at $31/oz, which means by default the silver resource/reserves will increase in the next resource update to reflect the increased silver (&lead) price(s) :-)