How so ddzx? You wrote: "therefore, if copper halved from its...

How so ddzx?  You wrote:

"therefore, if copper halved from its current US$2.30/lb and the exchange rate fell to 0.65, SFR would receive A$1.77/lb for its copper, where its total costs would be A$1.84/lb"

This is certainly not a correct assumption.  If the price of copper halved then input costs to production would also fall, and the mine would remain profitable.  This trend is self-evident already.  Furthermore if copper price halved, you'd take out the bulk of global production even with falling input costs.  Against whatever absolute metrics for price you want to set, the most profitable copper mines today with plenty of mine life, will still be in production to satisfy demand.  DeGrussa is one such mine.   If want to refute that, well OK,  maybe you do know F.A. then.