Forget about the ferrochrome quantity and price.
It can be simple as you state:
"340-million tonnes of chromite" times "Raw chromite fetches about US$200 per tonne" equals 68 billion dollars.
That answers the 60 billion dollar question.

HOWEVER, many as I, claim that there is much more than what is already known. I used the 3x guess, hence my 200 billion dollars.( from heaven to earth but maybe now into just the clouds?)

Sooo some must be using the 10X guess of the already known to get 600. May be ok, but I prefer to be more conservative until we get more drill results on the unexplored claims.

As to market, who says that you need to dump most of it on the market at the same time? and if you do not does that mean that the total value of ore is less?
I say absolutely not. And we can bet that the N.American market is more or less ours to have or lose. Only the remainder of the world market is a concern to us as to whether we can break into it ( just look at the troubles in S.Africa). If we produce less per annum then we need less processing capability saving some dollars up front. But do we care that much in light of the total value of ore. I say little.
The only significant cost up front is the delivery method, meaning railway and that is more or less fixed no matter how much ore is processed per any year.