Incompetence at being selfish.

They think they’re being selfish, but they fucking suck at it. They think selfish means “I don’t want to pay taxes but fuck you you still have to pay I win you lose”.

If they were even slightly competent at being selfish, they’d realize in about three seconds that doing things that way makes your town (and more) stressed out and shitty, and you still have to live there, and you can only build walls so high.

And even if we got rid of physics so you could build impossibly tall walls, now you’ve definitely lost because you had to build them in the first place, instead of being even remotely sensible and building a world where your neighbor would be happy to see you, or thrive peacefully and leave you be.

The “economics” of it are mostly about couching this damning and embarrassing realization in big words so that everybody stops paying attention because they yawned and lost interest.