I really got lost in your math. I looked over at figure 22.2, and I don't see how you can just take numbers from there and simply just add it back together. I assume it's a much more complicated model.
This is directly taken out of the FS.
The Project NPV is most sensitive to exchange rate and copper price followed by operating costs, capital costs, gold price, and molybdenum price. The IRR is most sensitive to exchange rate and copper price followed by operating costs, capital costs, gold price, and molybdenum price. The NPV and IRR sensitivities and provided in Figure 22.2 and Figure 22.3.
As you can see, the says it's biggest factor exchange rate and copper prices. No doubt that the drop in copper prices will affect the value. The project is still more sensitive to capex and operating cost than gold or moly prices which isn't surprising as Teck is looking into reducing that area of costs as well.
Honestly, this is all based on the JV moving ahead with the pit design by Tetra Tech. If Teck goes with a different operations, the economics will be different as well.