No company waits until the entire resource has been mined to recieve their payoff. Which is why resouces are generally sold at a percentage of their gross in-ground value. For example, if we have a resource which can be mined over 100 years, it might be reasonable to only take into account perhaps the first ten or twenty years of production when calculating a rough "value". Subtract costs of infrastructure, mining, transport, taxes, interest, acquisition etc. plus a percentage for actual profit, then you might have a ballpark figure.

So no-one(I hope) expects any exploration company to see anything like the total gross in-ground value of any deposit they find. With gold for example, they might realise 10% to 20% depending on things like location in a stable country, existing infrastructure, ease and costs of extraction and so on. With chromite things are less clear-cut with little precedent for any deposit even close in size and grade to those in the ROF area.

Who knows, 3%?1%? Still formidable numbers when you start with a big number like $300billion.