Arrium cost per tonne for Iron Ore is AU$71 or US$66
Look at the results (released 1 week ago) and mining (Iron Ore) segment analysis.
Revenue = $1,569m
EBITDA = $686m
Cost of goods sold (COGS) = $883m (i.e. 1569 - 686 = 883)
Tonnes = 12.5
So 883 / 12.5 = AU$70.64
Or AU$70.64 * 0.93 = US65.70