I know this is old but the way you have looked at NPV is correct... though its very hard to justify a $2billion spend for an NPV of $200m. It doesn't show that to be a good investment... yes you get your IRR back but do you want to risk $2b for an NPV of $200 + interest?
This is generally how equity (institutions) and financiers will look at this prospect. As a general rule NPV to Equal Investment is the ideal starting point.
