The way I think of storage is that it competes with natural gas peaking plants, not that it is part of the cost of renewables. Even if we had a lot more nuclear deployed, we would need a way to handle short-term variance in load, which is either gas or storage. (An interesting alternative would be scalable sinks for extra power; some people argue that this is why proof-of-work crypto is actually good, just use the extra power to generate hashes, but I would rather see it used for something more useful, like making hydrogen.)