luvtohunt, your insights are appreciated - yes I am late to this part of the EXS discussion.
One thing that may be different from the negotiations in which you have been involved, assuming that those dealt with fairly straightforward future projections, is the ability and in fact need to take future contingencies into account (if resource/reserve is at such level when at preliminary feasibility study, then . . . etc. and adjustments to terms of payback for carried interest through to production, etc.). I guess that is just saying there are even more variables due to all that is inherently unknown about resource/reserves.
There were many analysts that thought the premium Goldcorp gave for Andean was excessive, but they were only looking at released Ni 43-101 info whereas the companies negotiated based on their own models and projections. But that was a buyout offer. Negotiating an on-going relationship provides room for ways to make terms contingent on how some of the future uncertainties actually turn out.