While I have come to like those cost assessments...the guy does them for different primary miners (gold and silver I think)....showing a comparison of a few years worth of data for any one company might validate the numbers better. Also, unless I misread information...most silver is obtained from a co mining (and not even gold)....and global mining companies (like AU, eastern europe, and china/india) are not considered.
I think his articles are better for comparing mining companies to invest in, than defining a base global cost of producing silver
my two cents worth.
That said, I don't think we will see silver much below 24 either...just not because of that rather micro assessment of cost of producing