Uranium and even enriched uranium is still reasonably cheap. Fuel rods get expensive, and more critically only using up ~5% of a fuel rod before you need to replace it gets even more expensive. Other reactor designs can use a higher percentage of uranium without reprocessing, but they have other issues. In the end fuel including waste disposal represents about 10% of nuclear reactors operating costs or ~1c/kWh. It’s a significant but hardly gamebreaking cost.