Lets not get out of hand here... the simple fact is that they are looking to JV on 767mt out of the total 923mt that have been delineated so far.
767mt @ $0.20/t = $1.5b
Half that for a 50:50 JV and you get your rough $600-700m.
Also, $0.20/t is considered quite conservative when you compare to recent acquisitions.