"If it were possible to largely mine the massives first then the pay back to cover the capital expenditure on the mine would be done with quickly. Presumably over the years metal prices rise and it would be appropriate to mine the lesser quality ore later and still have nice profits."

You seem to have omitted the pge's. There is just as likely to be significant upgrading on the $ value. We may find that the Cr is a by-product of taking out the ritzy stuff being that we don't need a lot of it at the prices they fetch. It is my suspicion that they are just as excited about the pge's as they are everything else.