General Discussion, page-136

I think the most accurate way to calculate NPV for various SP6 prices is to use the table out of the DFS designed for that purpose
Having said that, not sure this table is designed to be extrapolated that far out.

The DFS was based on $1250 then $900, just using the more conservative $1250 figure,
SP6 at the current $5000 (ish) would be a 400% increase
For each 20% increase add US$1239.7m (from the table)
So thats 20 x US$1239.7m = US$24.794b on top of the US$2.9b (A$4.1b) post tax NPV
So US$27.7b or A$39 billion Post Tax (most quote pre tax)
Of course very unlikely to get that price over the mine life.

Someone handy with excel would be able to tabulate that for various spod prices