Ann: Half Yearly Report and Accounts , page-14

"388 million on 2 billion of capex is a 19% ROI"

Since when did capex on Jervois jump to 2 bill?
I think you confused capex with revenue?

From page 1;
"The study examined annual processing rates of 1.5Mtpa, 2Mtpa and 2.5Mtpa. It found that, at the 2.5Mtpa rate, Jervois will produce 181,000 tonnes of copper in concentrate, or pproximately 26,000 tonnes a year for seven years, plus significant by-products of gold, silver and magnetite, and provide free cash flow of $388 million (assuming US$ = A$) on revenue of $1.985 billion."