Ann: GOULAMINA LITHIUM PROJECT DEFINITIVE FEASIBILITY STUDY, page-109

Scarpa, not worth getting to carried away with any Company DFS. Inputs are just best guesses. Everyone thinks they are all 'Gospel' accurate but in reality they would be in the same basket as Economic and Weather forecasts for accuracy.
Selling price of Concentrate used is just a long term average forecast price of experts. Costs are best estimates/best guesses. Its difficult enough to prepare forward 12 month budgets in existing businesses so preparing estimates for a 10 year plus resource .......
But they are required to provide comfort for stakeholders and the market who rely on them to make decisions. Although if they were spot on you can bet the market would assign way higher share prices.
All they need to do is show the resource is way more than marginally economic to mine. In the end that is what is important. On the journey the business may or may not get lucky with better than estimated input costs and revenue. That is the importance of a great management team.
MLL were smart enough to get CHICO to check inputs to provide stakeholders and the market with a higher level of comfort. So not much point in non experts not able to access inside information picking on various inputs. Totally pointless worrying about a few $$$$ here and there..
Having the DFS enables a company to proceed to the next step.