-- Economic threshold analysis of the project on a joint venture basis
returns a 8.1% internal rate of return and an NPV7 of US$3.4 million
using zinc:
.80 $US/lb, copper $2.50 $US/lb, silver $12.00 $US/ounce
and gold $1000 $US/ounce with an exchange rate of $CDN 1.04 to the US
dollar.
-- The project is sensitive to metal prices, exchange rate and capital cost
as primary impacts. For example, a 10% increase in metal prices
translates to a 12 fold increase in NPV and a 2 fold increase in
internal rate of return.

Check out the low prices that are being used:

price used the real probable price

Zinc $.80 $1.10+
Copper $2.50 $3.50+
Silver $12 $20+
Gold $1000 $1300+

a 10% increase in metal prices
translates to a 12 fold increase in NPV and a 2 fold increase in
internal rate of return.

What about a 30%(or more) increase? We're talking a 36 fold increase in NPV here and a 6 fold increase in the internal rate of return.
Are you kidding me? Donner is going to be sold very soon. I dont think Xstrata really wanted to share all this but due to the terms of the JV, they had to.