I just realised that I made a basic mistake by simply doubling...

I just realised that I made a basic mistake by simply doubling their valuation. Why? Because cahs costs used in the report are US$ 676 and US$ 1,50, and higher prices improve profit a lot once we are above that level.

If you use their numbers:
US$ 1000 - 676 = US$ 576 profit / ounce for gold and
US$ 2,5 - 1,5 = US$ 1 profit / pound for copper.

At current spot prices
US$ 1586 - 676 = US$ 910 profit / ounce for gold and
US$ 4,5 - 1,5 = US$ 3 profit / pound for copper !!!

Bullish scenario :
US$ 2000 - 676 = US$ 1324 profit / ounce for gold and
US$ 5,0 - 1,5 = US$ 3,5 profit / pound for copper.

So, at current or higher prices our earnings from copper will be at least 3 times higher than expected by the report.
If, otoh, the world economy tanks and QE3 comes into play, gold prices will go up to US$ 2000 or more and we will make a killing with Hera ... Nice inbuilt hedge, isn't it?