I agree, there are better options for mass scale long term energy storage than batteries, e.g. (green) hydrogen, methane
Pumped hydro is currently the cheapest long term energy storage by a significant amount.
not so cheap anymore when you want to add lot's of storage capacity
That's exactly when pumped hydro shines. Increasing the storage reservoir capacity is cheap. It's the turbines and infrastructure that's expensive, but that doesn't change if you're only increasing the capacity.
Pumped hydro is currently the cheapest long term energy storage by a significant amount.
not so cheap anymore when you want to add lot's of storage capacity
That's exactly when pumped hydro shines. Increasing the storage reservoir capacity is cheap. It's the turbines and infrastructure that's expensive, but that doesn't change if you're only increasing the capacity.