adani aust. head quits $11 bln coal project, page-6

I find your model hard to comprehend with your statement that the "coal price doesn't matter".

I note you've mentioned a $2 index, but what happens if mining costs go up and coal prices come down eroding profit margins?

Profitability, ROI, IRR and payback periods are all affected by the coal price.

Your statement doesn't make sense at all.