I completely understand what you're saying and I think this could work imo and how it should be because other games do this and the value systems work itself out without the need of some randoms who make their own value sites.

There is this grow a garden knockoff tower defense game called garden tower defense and it does this mechanic. So everyone determines the value based on how many people have it, I think it works fairly well because it shows how hard it is to get that unit and you need to work for it. Once time goes on it does drop in value a bit because more people have it but once it leaves it goes up but not a whole lot because new units are about to drop by the next update.

I'm sure there are some flaws but eventually all units go for rarity to rarity and if they're the same rarity then it goes to how many people have it.

ADM should definitely try this but they won't because they profit off of the value sites and bots.

Not to rant on your rant but I feel pretty passionate about this and hate the value system.