Is not the definition of insanity is doing the same thing over and over and expecting different results?

When building complex infrastructure for the second/third/etc. time? Of course not. Economies of scale is the term you're looking for.

Hinkley is the fourth time, still no dice.

When has nuclear ever had economies of scale?

Do you have any examples of a very high cost reactor dropping by a significant amount on a subsequent build?

South Korea was able to eke our small decreases in cost (though some people have ended up in jail for falsifying record keeping). But otherwise, costs tend to rise. And I'm definitely not aware of a drop of 50% or so, to bring these excessive costs into the realm of competitiveness.