France was able to output 2 reactors per year at 1,5 billion of euros per 1000MW for more than 2 decades during the 70's to 90's. The whole French nuclear industry has cost around 130-150 billions between 1960 and 2010, including researches, build and maintenance of France's whole nuclear fleet.
A 1000MW reactor, at current French electricity price and for a 80% capacity factor, generates 1,4 billion of euros worth of electricity per year, for a minimum of 60 years.
Nuclear is not costly, and can absolutely compete by itself, if you don't sabotage it and plan it right.
Besides, it's not a technical limitation on nuclear power, it's an ecological measure.
The hole in production was due to a corrosion problem detected in several reactors, which occurred at the same time as maintenance work in other reactors that were behind schedule because of COVID. This would have had no impact if nuclear power had not been left virtually abandoned for 30 years because of the anti-nuclear movement.
It's the classic story: anti-nukes shoot nuclear power in the foot, then claim that nuclear power doesn't work, despite reality.