It wasn’t $40-50 billion. It was estimated to cost $116-$600 billion to build 7 nuclear reactors https://smartenergy.org.au/nuclear-fallout-116-600-billion-t...

I think the likely cost would have been hundreds of billions considering Australia does not have a nuclear energy generation industry. It currently has a very small nuclear workforce as it only has a small nuclear medical reactor on the outskirts of Sydney.