If you actually look at what the $70 price indicates, it is not...

If you actually look at what the $70 price indicates, it is not what BAU have (released publicly at least).
To quote the price index is:

CBIX is "value in use" CFR reference price for a standard gibbsitic bauxite (5% reacting silica, 10% moisture, 50% reacting alumina - 5/10/50) which reflects the market conditions for bauxite imports into China. Each CBIX value is a 30 day rolling, value in use, trade weighted, average price of a representative sample of bauxite imports into China over the period.

http://thebauxiteindex.com/cbix/about-us-cbix for more.