I have to respectfully disagree. I don't think a car is necessarily worth the added-up cost of the various items that went into it, although some may be. As many, myself included, have found out, it is easy to get 'upside down' in projects, especially limited-appeal projects like GT40s.
Of course they appeal to all of us here, but that's why we're here; most people aren't interested and the resale market is small.
The problem with doing a car like an ERA on spec is that most people, for that kind of money, want things exactly as they choose, not 'close' to what they would have picked on their own. (I think this is why so many GT40s get repainted.) I think a fully done ERA is not worth 120K or anything near it; I think 85-90 is a lot closer to the mark. After all, you can get an RF finished out for less than that, and it is every bit as good a car as an ERA, with fit and finish at least as good.