Ultimately though about 50% of the cost of a PWR is in the heat handling (heat exchangers and steam turbine) and the building costs to accommodate those systems. If the nuclear part was free they'd still struggle to compete -- the BWRX300 seems to get a lot of cost reduction by eliminating the pumps and heat exchangers and stuff and going to steel-concrete sandwich construction but to do better than that you have to really do something about that steam turbine.

For that matter, it's shocking how small the actual core is for FBRs. The capital cost of FBRs was long projected to be higher because traditionally you had to add a third cooling loop and some other systems but it is projected an sCO2 system today could be cheaper overall.