The way I do it is like that.

E.g. Y1-7: 403.9Mlbs CuEq x (($3.15/0.77) - $1.50) = $1046.47 Net Cash Flow

The sustaining is included in the $1.50 total cost.  I only use a sustaining number to calculate the payback time (capex + sustaining) / $1046.47

For the rest, I use a compounding of (2) in the calculator and capex is -400 Y1 and -800 Y2-4, but there's no good or bad answer for that, it's anyone's guess.

Let me know if that helps.

IMO.

MoneyK