Everything new is super expensive.

A Cray 2 cost 12M when I was a child my S21 Ultra cost 1200 dollars and is 850 times as powerful.

The first functional fusion reactor (if it is ITER) is going to be outrageously expensive because it is all custom built on site like nuclear reactors are.

Fusion has an advantage though as it won't puke radioactive waste everywhere so they will likely be built factory style and assembled on site.