Considering a single reactor costs €11-19 billion[1][2] to build in Western Europe currently (Olkiluoto 3, Flamanville (we haven't seen the final bill for that one yet)), an additional 300 million dollars is a drop in the bucket and not the thing that will make the project go from viable to nonviable.
Step 1: Nuclear reactors are so expensive already, additional costs to increase safety barely matter in their overall price! This additional regulation isn't enough to make a viable plant nonviable.
Step 2: Nuclear reactors are so expensive it makes no sense to provision new ones when renewables are just around the corner! Just keep the current coal power plants running while we take another decade to increase solar grid capacity by a few terawatts.
Step 3: Go to step 1.
See also; heap fallacy. Seriously, coal power generation is so bad that if we had to reduce safety regulations to the point that we were having a Chernobyl-level meltdown every month to replace all coal with nuclear plants, we would be significantly better off for it. It's not even close. We could literally completely deregulate safety of nuclear power plants and be safer overall.
(Per the stats I shared earlier, coal power kills 100,000 people per thousand terawatt-hours produced. The world produces roughly 44,000 tWh of coal energy, resulting in 4.4 million deaths per year. Casualty estimates of Chernobyl vary wildly, but even the most pessimistic estimate produced by Greenpeace, avowed anti-nuclear activists that they are, only totals 200,000. Coal power is almost twice as bad as having a Chernobyl every month)
Considering a single reactor costs €11-19 billion[1][2] to build in Western Europe currently (Olkiluoto 3, Flamanville (we haven't seen the final bill for that one yet)), an additional 300 million dollars is a drop in the bucket and not the thing that will make the project go from viable to nonviable.
[1]: https://en.wikipedia.org/wiki/Olkiluoto_Nuclear_Power_Plant#... (final)
[2]: https://en.wikipedia.org/wiki/Flamanville_Nuclear_Power_Plan... (projected, not final)