I don't think the multibillion price tag is about the physical battery itself.
It's probably the cost of the entire project. Which includes:
- Project management
- Engineering
- Digging the whole
- Security
- Maintainance
- Environmental impact analysis (among many other analysis)
- Reducing the environmental impact
- Permits (and a LOT of bureaucracy)
The list goes on. Notice how I didn't even mention the battery itself.
That explains why everyone in anime seems so fucking dumb.
"In order to kill the guy, we have to shoot him in the head"
"So you are saying that we have to shoot the guy in the head in order to kill him?"
Yes you little shit, that's exactly what he said, with the exact same words. It's so annoying.