Wow. I'd seen renders of the proposed magnet geometry, and it looked like a nightmare to build. They actually built it successfully. It was built by welding curved parts together, not 3D printing the thing in metal. It uses a superconducting magnet, which means having to wind coils from somewhat brittle niobium-titanium alloy. These are strangely-shaped non-planar coils which operate at liquid helium temperatures a few centimeters from 100 million degree plasma.

Here's an industrial view of the construction project.[1] Considerable new manufacturing technology had to be developed to build this. One minor component is a diamond window 120mm across and 1.8mm thick, soldered into a stainless steel frame with copper-silver-titanium solder.

Cost €370M. Look at the construction pictures and you can see why.

I wonder how the Skunk Works fusion project is coming along. They have an even stranger geometry. The only word out of Lockheed is that there's been enough progress to justify spending more of Lockheed's money on the project.

[1] https://www.ipp.mpg.de/987655/w7x_and_industry_en.pdf