Hi warrantless,
It's a guess (no calculation was done) based on what have been spent on large mines mines from start to poring the first gold bar.
I imagine that the total costs would include, but not limited to the following: producing a BFS by an accredited consulting firm (the banks would want to see this report), permitting, engineering work, project management, equipment procurement, labour costs, initial preparation to get rid of the overburden, digging the hole, building the processing facilities, infrastructure, etc...and surprises.
I would say $450 to $500M would be an underestimate (depending what's included in the analyst's calculation, and I would tend to believe the number from a formal NI-43-101 compliant BFS than a number from an analyst) judging from the money Barrick/Gold Corp spent to build Pueblo Viejo gold mine in Dominican Republic (some $3.5B). I would expect the mine developed for Borden would be smaller than Pueblo Viejo, but we still talk billions (not hundreds of $M). And, I would not be surprised to see at least about $1B. Even a shallow open-pit graphite mine with simple processing facilities would cost about $150M.
The development cost of the large Cu/Au mine in Mongolia has escalated (there are always surprises) to something like $8B which required IVN to enlist the help of Rio Tinto as a partner to finance the extra $B. Eventually, the legendary Robert Friedland ended up losing the company to Rio (SP has gone from about $28 to $8.7).
The point here is that, whatever it is, it will be big bucks and would be beyond the ability of for PRB to raise without taking in a senior partner who would foot the big bill for a large (or eventually all) stake in the company. I would sell the Borden Gold project if the price is right, take the money (and run?) or use part of the proceeds to do something PRB is good at...i.e. exploration (on the rest of their claims.
Hope that would provide some rationale for my saying billions.
goldhunter
