Good question to take seriously. But you got me? If the simple answer is "things that money just can't buy" that would be a metric which ends up being equally

Good question to take seriously. But you got me? If the simple answer is "things that money just can't buy" that would be a metric which ends up being equally gamed before you know it. Like anything else. How would you avoid that while remaining simple? Well people may not want to take money out of the equation, but sometimes it cancels itself whether it appears on both sides of the equals sign or not :\ Which probably reduces to "the best metric is not an accurate measurement". This in itself is apparently realistic even though it has not been proven in all cases. Now there could be further simplification to a corollary; "the best metric is not a measurement" :0 But only over the limited range where P <> NP. Or it could get more complicated than it already is.