As such the way I have calculated costs in those above workings is correct as the total cost has been accounted for. If we were to use costs spread across ounces produced rather than ounces sold it brings the real costs down to $673.70. When you multiply that by 46,855 ounces 31,566,213 (allow small error for rounding) i.e the same number for costs.
Interestingly enough the note says it also allows for costs of ore stockpiling etc so that is another cost that can be ticked off the list as not being a reason for the cash going missing.
BDR Price at posting:
46.0¢ Sentiment: Hold Disclosure: Held