[azernik]

The parameters that go into the efficiency/gain of a power plant are well known: gain goes up as radius to the power of 1.3, and magnetic field strength to the fourth power.

ITER was conceived in an era of much lower-field superconducting magnets, so it had to increase the size instead. This massive size has been the big cost and schedule driver.

However, since ITER was designed there have been big advances in the production of high-magnetic-field superconductors. These are really recent - ReBCO tapes have only started to be sold by commercial producers in the last year or two. With higher fields, we can get performance equal to or better than ITER at much smaller size (and hence price). This specific effort is an MIT project, relying heavily on MIT research in building magnets with the new superconductors.

I highly recommend this video for a look at the different scaling factors: https://youtu.be/h8uYNhevRtk?t=571