Ann: Maricunga Definitive Feasibility Study, page-76

Unfortunately that is the not the cost estimating model when running a big project. 
I am a project professional in IT  but estimating approach is still the same. 
It is what it is.  Financers will send a team of analysts to study the costing model before they ink anything.
A dodgy project will always underestimate things hence they never get into production. 
they just suck retail holders into the game whilst insider sold out for big profit.