I'm not sure I understand the question. It's always cheaper.
No it isn't. Storage capacity for energy is expensive, if you want to have a grid that is largely dependent on intermittent sources and still have a stable grid providing power at all times you need large amounts of storage as well as generating capacity.
For example if nuclear costs 1bn for a GW and solar+wind costs 0.6bn but you need to also install 0.5bn of storage to make the grid reliable to the safety margin you deem acceptable then it is no longer a cheaper system.
Amount of storage needed scales up rapidly as you get towards an grid with entirely intermittent generation.
What are you smoking??
Storage is more expensive than generation. Always.
We see some storage on the grid because storage is fast. Batteries can respond to load changes a lot faster than anything else. Demand goes up, the batteries are drawn down while cheaper generators are spun up. A few places use pumped hydro for the same purpose, but that's very situational.