I went looking for operating closed cycle gas turbine power plants- this seems like a research topic all on its own, no matter the heat source.

It's definitely true that simple cycle gas turbine plants are much cheaper than equivalent size steam plants. This right here sets the bar for any kind of thermal power plant.

See table ES3 for cost comparisons..

https://esmap.org/sites/default/files/esmap-files/TR122-09_G...