VS the cost today yes. Nuclear wasn’t seen as a prohibitively expensive form of energy, quite the opposite. South korea and China are making it work. But if you build a new prototype every time and get bogged down in decades of environmental surveys, lawsuits and ever changing over regulations, any infrastructure project becomes prohibitive, whether it is nuclear, high speed rail, or anything else.

It led to onsite cost reductions. But these were negated if the following site had serious design changes. Example is France. Still, compared to today it was much cheaper.

There are some european success stories in high speed rail too (France). China doesn’t let itself entangled in planning restrictions. US and European countries love over regulation and litigations. That’s a choice, and it comes with a steep cost.