Otherwise you're being mean and unfair.
So yes, you do need to actually base the cost on the worst case scenario.
So how much does enough storage to cover a months long unplanned nuclear plant outage cost?
The financials for nuclear are truly terrible. At least when it was the cheapest source, the proliferation risks and highly centralized aspect seemed counter-balanced.
Now there is no upside, and they literally just bribe politicians for subsidies.
And making gains on nuclear would take decades, while solar would continually be rolled out and improve that whole time.
Dams cost less than nuclear. Tvindkraft was the first MW scale turbine in the late 70s and cost about $5 in 2022 dollars per net watt. An investment to the scale of the manhattan project would have gotten us past where we are now at any point in the last century.
We will probably never need to store 100% of generated renewable energy. Storage would probably need to be a small percentage of the generation capacity.
https://reneweconomy.com.au/much-storage-back-high-renewable...
This link seems to indicate that the need grows non-linearly. Existing storage is sufficient for 30-50% penetration, whereas it grows to about 20% when it reaches 80% penetration, only hitting 1:1 in the worst case regions for 100% penetration.