Storage is almost entirely capex, not opex.

So yes, you do need to actually base the cost on the worst case scenario.

Wrong. Storage has opex, because it has energy losses. Not all the energy that goes in can come out. 2nd Law and all that. On top of that, there will be maintenance and operating staff costs.

Worst case scenario, huh?

So how much does enough storage to cover a months long unplanned nuclear plant outage cost?

A perfect summary of every pro-nuclear argument.

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.

Even when it was "cheapest" it still wasn't really. It was heavily subsidized directly and indirectly by the public and by parts of the supply chain built for military purposes. Even after all that, costs only appeared low because of all the corners being cut. As soon as the industry was held to actually put in place all the safety measure they claimed, prices skyrocketed. Uranium mining in developing nations is still not held to any sort of environmental standard, and the mines in france, canada, ussr, and the usa were never cleaned up. The tailings that weren't just dumped into watersheds on native or lower class land were just half-heartedly covered with a plastic sheet. We're still playing hot potato with th waste from the time, too.

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.