It is not a bad metric of value, it is just an incomplete metric of value. It includes only the price and hours played. You propose including additional factors to make it a better number, but how exactly are we all going to collect the level of enjoyment, playability, and non-cheapness as numbers we can plug into a formula?

Including or not including player count will skew the pool one way or another, but they are still interesting numbers to look at; and someone who is trying to fill the most time for the least dollars absolutely should watch this metric.

Comparing your collection to this time and money formula will help highlight what you do and don't like in board games independent of price or replayability.