I am not sure where the sub $1,000 came from but from the 43-101 I think the rough numbers used there were in the the $1,600-$1,700 per tonne. Those may have been considered conservative but we also may have added some cost in order to get a higher purity or some specific flowsheet characteristics needed to obtain a higher selling price.
What is more importnat than just the cost is the spread between the selling price and the cost. For example, I would rather sell at $13,000 and have a cost of $2,500 then sell at $8,000 and have a cost of $1,600.
The PEA should clarify all this.