We don't need "something" to make storage cheap. Storage is cheap, and is getting cheaper.
Again, we are not building storage out yet because we don't have enough renewables to charge it from yet. Instead, we are right now building out factories to make it. E.g., the factories to make iron-air batteries, $20/kWh, are under construction right now. Ammonia synthesis plants are under construction right now. Tankage for ammonia is dirt cheap. No breakthroughs needed, just build-out.
When we do get to building out storage itself, it will be cheaper than it already is.
