You could buy it cheaper from AIG, but then they would never intend to pay off. So you are back to the funny money insurance and your tax dollars.
There’s a designated insurer just for nuke operators, and here’s their website:
http://www.nuclearinsurance.com/
I read somewhere else that a typical annual premium for coverage is $400K/site. That’s just the primary insurance, then they’d need a secondary policy. Dunno how much that would be.