Ann: Excellent Metallurgical Results - Greater Duchess Project, page-25

'saw Caravel using US$2.37 a pound for their PFS, but that's for a lower-grade, higher tonnage deposit. I can't find other comparables in Australia.'

A bit early to work out costs IMHO as there are many variables , ie what is the grade , what is ore body size , ie the bigger the plant the lower the cost per tonne of ore processed on an OPEX basis
Then Really need to know the Bond milling index of this ore for a plus 90% recovery to get an idea how it would compare with another base metal project BFS using flotation , and on a tonne of ore processed then multiplied by the % of ore to get the energy used per #
You could guess the the BMI was around 12 for this to make a rough stab, and then multiply the cost they are getting energy at ie gas or electricity at costs .
On the flip side with these sort of recoveries it could end up going with heap leach , and make copper cathode .
Could compare to a project like ASX listed G1A,s BFS (which I hold) just for a bit of day dreaming fun.
The above is what I would do , if fixated by CNB but I have no professional experience .