There are very significant economies of scale when increasing...

There are very significant economies of scale when increasing plant capacity. So plant with half the capacity will cost much more than half.

Then why not build the bigger one? Presumably capital is too scarce/expensive.

Changing the subject, the following is an interesting passage in the 2007 Annual Report. Interesting because Sillitoe is, I understand, not easily impressed. Granted the comments are quite guarded...Nevertheless.

"I for one was delighted to read in the report of one of the world experts in epithermal gold exploration, Dr Dick Sillitoe, the description of our new gold-silver discovery at Eureka as “a significant new discovery in the Deseado Massif for which the project team has to take full credit. Although exploration is still at an early stage, it is already clear that the veins are locally of exceptional width as well as containing potentially ore-grade precious-metal values. The geologic setting alongside a rigid porphyry body, unique to date in the massif, may have contributed to the exceptional vein widths."