Part of that cost is from ITER being so huge, which is because they use obsolete superconductors. CFS is doing the same thing in a reactor a tenth as big, using newer superconductors that support stronger magnetic fields.

The size and also the complicated governance have made ITER very slow to build, which also increases expense. The JET tokamak is about the size of the reactor CFS is building, and JET was built in a year for the reactor itself, plus three years before that for the building they put it in.