https://www.publicpower.org/periodical/article/energy-storag...
https://www.lazard.com/media/2ozoovyg/lazards-lcoeplus-april... (Page 15 on for battery storage costs)
TLDR Batteries get cheaper before your pumped hydro at scale gets built. It’s what’s playing out in Australia with “Snowy 2” currently. Similar to how you could never build nuclear as fast as solar (almost free at utility scale) and batteries, not as cheap (based on experience curves).
Batteries also provide grid services (maintaining voltage and/or frequency) within hundreds of milliseconds of detecting an anomaly, which simply isn’t possible with spinning mass due to inertia. This provides valuable grid services revenue (distinct from energy arbitrage).
https://www.eqmagpro.com/snowy-hydro-2-0-more-expensive-than...
https://www.teslarati.com/tesla-big-battery-hornsdale-austra...