It’s also expensive because, for example, as described on the product page:
Section 508 of the U.S. Rehabilitation Act requires that Federal agencies' electronic and information technology be accessible to people with disabilities.
The Half-QWERTY 508 Keyboard is specifically designed to satisfy all compliance requirements for keyboards, under Section 508.
This is mostly something being bought by employers (e.g. federal government agencies) for employees with disabilities, partly for regulatory compliance reasons, and there aren’t many competing products.
if I was Matias, I would buy up some Ergodoxen and experiment making their one-handed keyboard with that technology. It would vastly reduce their costs, for one thing.
How would that reduce their costs? The tooling, electronics design, and distribution are the expensive part of producing this product; the incremental production cost is probably similar to any other keyboard made at a similar small scale.
If they wanted to make a mechanical-switch version, they could maybe use half of their new ErgoPro keyboard for it. Even then, redoing all the electronics is going to be expensive and take a while.
Considering that they have staff that already knows how to design and make a keyboard, I am sure they could find a way to make the Ergodox PCB Alps compatible (somebody already has, haven't they?), make some adjustments on PCB to optimize for one-handed usage, throw together a case, tweak the firmware, and then BOOM! you got a keyboard.
I know it's harder than I described, but it can't be that hard, can it?
It’s not “that hard” to design and build a prototype with just a PCB, a layered acrylic case, and a general-purpose microcontroller board like a Teensy. (The Ergodox is basically that, a prototype, meant for DIY hacker types.) But it is hard to make a real product with the design, manufacturing, and distribution that goes along with that.