I think you bring up a good point. These metrics, formulae, etc. can only be applied when thinking about new features. When building the core product we must rely on our knowledge of the market/users to decide what features end up in v1.0.

It is also prudent to bake in anonymized usage tracking code so you know how users are using your v1.0. This will provide a guideline on what area of the product to concentrate on when thinking about new features. This way we don't end up spending time pushing out features that few will use when our data had showed we should be concentrating on a different area of the product.