Yes, all three. Building a nuke plant without the additional concern for outcome that we put on nuke would be relatively inexpensive. It's just concrete, pumps, and a turbine. It's a ismilar level of complexity to a coal plant. Same with running cost, same with decommissioning costs.
https://en.wikipedia.org/wiki/Kingston_Fossil_Plant_coal_fly...
Suppose we designed, operated, and budgeted every coal plant to make accidents like this a statistical impossibility. Not very unlikely, that's not the standard we hold nuke to. An impossiblity. Imagine what that would cost.
Even if you ramped down the safety, it still wouldn't be cheap or simple.
Industrial control systems are fundamentally sensors, actuators and a computer. None of those is actually that expensive. Nobody should be paying a billion dollars for a valve.
Older reactors have somewhat high operating costs because they're so old, many of them were built more than half a century ago. Newer reactors often have higher costs because of the lack of scale. If you only build one or two of something you have to amortize the development costs over that many units, mistakes that require redoing work are being made for the first time, etc. Build more of them and the unit cost goes down.
These are what makes it cost 5x solar or wind.