The reactor itself takes a long time to ramp up and down, but it heats a molten salt battery. The battery can burst-power the turbines at well-above the reactor output; they can be sized to handle peak demand + overnight loads.
It's hard to find current numbers, but capital investment for combined cycle natural gas plants seems to be about a tenth of modern reactor projects in western countries.
The plant designs I’m describing are new, but marching to commercialization. They are not in wide-scale production yet.
They are optimized for a world where solar and wind have taken over most of the production.