The way I see it, VD is expected to produce 85Mlbs per year. Assuming copper at $3.15 US and total cost around $1.50 US, that's $1.65 US of net cash flow per pound or roughly 140M US per year for 14 years. To keep this easy, I'm not considering years 1,16,17,18, because I don't think they would reach a 85Mlbs production. For capex, I'm estimating a two year construction at 115M per year (total 230M).
If you discount the stream of cash flows at 7.5%, that should give you a pre-tax NPV (7.5%) around 800M US.
I'm hoping somebody would be willing to pay 50% of the pre-tax NPV (7.5%) for a PEA stage project, but I don't have much data or examples to back this up. An investor will probably look at the global IRR for the acquisition + project.
Don't forget that these figures are only considering copper at $3.15 US. Also, there's a lot of potential to drill and increase mine life. That's a lot of upside for a potential buyer.
MoneyK