Actually no. You need to apply high school Algebra. Because the...

Actually no. You need to apply high school Algebra. Because the production is in oz and AISC is $/oz, dividing the production by AISC gives you square oz and then dividing the EV by the result, you create $/square oz. I cannot see any meaning in that. I guess you are trying to allow for AISC as a cost in your measure but I think you would do better simply by subtracting the AISC from the EV/Production, in which case you will get $/oz with the AISC impact removed. To use your example,
$600m/200,000oz - $1200/oz = $1800/oz.

Interestingly, if you do that, some companies like RMS, GCY and BLK come out with negative values, which is a reflection how little the market appreciates those companies at present.