> “We shrunk the sensors and got high fidelity signals,” Chung says, “by figuring out novel ways to fit more powerful sensors into tight spaces.” Some of that had to do with the arrangement of the magnetic material, he says, but can’t say more until patents are filed.

Which is interesting. I guess the main component here is manufacturing cost, since very small, very high capability probes exist since the ~60s. E.g. Tektronix has had small probes with 50-100 MHz [which is orders of magnitude wider than you'd need for this] bandwidth since then.