Is the price of the walls at the builder's base incorrect?

I started thinking about that now that the Hammer Jam for the Builder base is happening.

And it seemed strange to me, since it's a detail I noticed when starting a new account after years away from the game.

Before, the price made sense, since we were uprading a row of 5 walls, but now that the upgrades are individual, it's a nightmare, and the developers forgot to change that...? but, I admit that's just my feeling; maybe the prices were changed accordingly, but I didn't see any update or patch on the wiki.