RE: Northern Dancer vs. Mactung You don't need to try to figure out infra, capex or production cost related stuff by yourself. PEA are out for both Mactung and Northern dancer.
IRR's are quite similar: 23,5% Mactung, 22,2% ND (using $300/MTU)
Initial years production costs: somewhat over $100/MTU both
ND net present value is about 3 times larger than Mactung's. But Mactung might be able to show higher NPV if scope(=capex) of project would extended.
While Mactung has much higher grade, it is underground operation which make the projects more or less equivalent cost producers.