Well there are the standard metrics of DAU's, notes, etc; although I take the point of the inherent difficulty in doing this with as fragmented and open of a network as Nostr.
Daily Zaps are another, perhaps more direct and literal indication of "value" accrued to the network.
Usage numbers are like GDP, they only indirectly correlate with real value ("wealth"). Assessing real "success" in human terms requires us to adopt a measure of human flourishing that is subject to an over-arching qualitative framework of value.
Well "usage" and "zaps" are distinct, the latter being a better reference for value and/or wealth.
I agree that it's economic value, but I would still argue that that is a reasonable framework for assessing the value of a project. At the risk of being "vulgar libertarian" about it, I do think that freely-traded economic value is a rough proxy to how important a thing is to society.
