So what changed in cost? Safety and public perception. Getting plants approved to run need public forums...which causes delays... which costs money. Lots of money. We can build a plant in 4-5 years, but the NIMBY public backlash drags that to 8+ years. Planning commissions and local governments going back on their word and the like. It's circular logic. Naysayers say it's too expensive, but then place restrictions on the plants that no NG or wind farm would have to pass.
That's really not correct. Let's look at at the last three nuclear power projects in the US:
Progress Energy Levy Power Plant in Florida. Siting was at an existing nuclear plant and was 100% approved all the way to the governors office, and once all the eyes were dotted and all the tees were crossed, and all the NIMBY backlash had been put to bed, a rate hike was granted to pay for future production. Once construction started, there were cost over runs and delays, and more cost overruns and delays, and another rate hike was need to pay for all the new future costs so that was passed, and now there was a bunch of new money there were more cost overruns and delays...at which point the utility commission concluded it would cheaper to simply build new gas-fired plants rather than pay for the costs to finish the existing project.
Summer Nuclear Plant in SC. Again this was an expansion of an existing nuclear plant. Siting was 100% approved through the top level, so all the NIMBY backlash was put to bed and construction began. Consumers graciously agreed to a rate hike to pay for electricity they wouldn't get to use until years in the future. Once construction started, there were cost over runs and delays, and more cost overruns and delays, the contractor went bankrupt, and finally the utility commission concluded it was cheaper to simply walk away from all of the billions of dollars already spent than try to finish the project.
And finally Vogtle 3&4. Again, an expansion of an existing nuclear facility. After all the siting was 100% approved through the top level and construction began, the cost overruns started. There was delay, after delay, after delay. The project came this close >< to being canceled, and managed to squeak through on the strength of new investor money. And then there were more delays and cost over runs. If the project is eventually completed, the power will be amazingly expensive compared to say, natural gas.
Surely, the process added cost. But in each case, the cost increase problems started after the process was completed. And it is a false equivalency to suggest that wind farms get unfair treatment. Those projects have lots of process too. NEPA, SEPA, all that. I know first hand. That said, if a wind turbine falls over, that's a different outcome than a Fukushima-style meltdown. So it is entirely reasonable there should be a higher level of scrutiny for a nuclear plant than a wind farm.