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.
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.