I want to clear something up... there are about 31.1 grams in a TROY ounce ( which is what we want to look at). the 28 grams that has been talked about is just a regular ole ounce... the troy ounce is where Joeiniowa got his original calculation from which is correct.
Where did you get the $350 per ounce extraction costs per ton? I am interested in costs when figuring out what concentration is profitable but have not found many reliable sources.