You'd want to include cost in a similar way to medicine and other engineering areas do.

Doing X (new medical procedure, changing a road intersection) would save Y lives for Z cost.

If the cost Z is low you can shift resources to it from areas where cost Z is high per life or QUALY (quality adjusted life year) saved and overall save more lives.

Yes exactly. Nuclear regulation has had diminishing returns on safety for probably 50+ years. Are newer nuclear designs safer than they were in the 80s? Yes. Are they _enough_ safer to justify the increased cost relative those older designs? Almost definitely not. In the same way, we _could_ make wind and solar and coal etc. as safe as nuclear currently is. But it would _dramatically_ increase costs. That was my entire point. Nuclear is only not profitable because it's competing with generation technologies that are not required to meet the same safety standards.

The US nuclear regulatory regime _explicitly_ does not include costs when determining if a new regulatory rule is necessary. Any amount of safety at any cost is always justified. No other generation technology has that mindset.