Having recently installed a battery, I'd say they are definitely not cheaper. There is no way that residential battery storage can match the cost per kWh of utility scale storage.
At much less per house you can build massive utility scale storage, like pumped hydro.
However, these are complementary technologies, serving different time and scale of energy storage and duration. Home batteries aren't realistically going to solve storage on the weeks to season timeframe. They function on the order of hours to a couple days, and during local distribution outages.
Building grid scale storage still means grid itself needs to be updated for the increasing loads and spikes.
And I'm talking here smart batteries - controlled by grid owner. How it's not default (including solar, cars and other high load devices) it's a bit of a puzzler. Sure it's like 5 minutes of inconvenience for the owner, but saves trillions of dollars.
