Building one power plant is incredibly expensive. Building it again costs less. Building it 1000 times costs much less per plant. We're not building thousands of fission plants because of politics. Fusion might be an easier sell.
This isn't really true. Yes first of a kind is expensive and there is learning curve, but learning is serial and iteration cycle is long. You can't build 1000 plants in parallel and learn 1000x. Solar power cost is falling fast because iteration cycle is short.
South Korea built 28 reactors over 36 years and cost fell 1.5% per year, totalling 40% reduction. Even with this South Korean nuclear power is only about as half cheap as solar power locally (as of 2020), and South Korea is a very poor country for solar power considering its latitude and weather.
