That's the bare minimum for a single unadorned hole to that depth (? there's a lot of detail in the linked report, costs may blow up a bit as depth increases, that detail didn't leap out at me).

It would cause me no great surprise if "a sufficient hole"; widened, maybe three actual close holes for down pipe, up pipe, and reactor vessel, with casings and head mechanics, came to $50 million.

Your point stands, in the great scheme of capital projects of this scale the hole boring and fitting is cheap.

Sixteen odd years ago I tracked, with a group, every global mineral exploration activity and subsequent development. When it came time to launch a mine, deemed to be feasible, and raise forward capital for building plant and processing our lower bounds cut off point was $50 million US - anything smaller than that was too small scale to bring to the attention of our subscribers.

Capital costs for mining plants, power plants, oil and gas extraction run high - and the G20 costs for nuclear plants are fully in the billions.