Also, can't rule out the impacts of a time of high inflation...

Also, can't rule out the impacts of a time of high inflation across the globe affecting all goods and services not to mention uncertain geopolitical and economic factors surrounding rare earths. With ongoing design optimization and better economic conditions when project funding is required costs could be reduced. I think MEI have allowed a generous 35% contingency to cover themselves in the event of any unforeseen expenses. And with that, building a tailor-made mining and processing operation costs money and according to the study so far, they reckon potentially ~$403M.