These look great and I don’t doubt it’s worth the investment, but holy hell $500 is a tough price tag to accept.
I've settled on keyd[1], after using XKB and interception-tools for a while.
In that time, I’ve had 3 desks, 5 computer chairs, and 7 computers.
My view on it is, a good keyboard will get several years of use out of it, the average yearly price isn't really that much. Second, it's something I'm touching several hours most days of my life. I'm using a keyboard more than I wear shoes personally (I do prefer the barefoot life, so I'm a bit odd there). I'm touching it more than my couch or my dining chairs or other things in my home. Isn't it worthwhile that it's comfortable and exactly what I want from it?
And as such, I'm an extremely satisfied Advantage 360 Pro user. The Adv 360 + a mouse side-grade massively reduced pains in my hands/wrists to the point where I don't notice any issues 99% of the time, even with heavy (7+ hour) computer use and quite a lot of FPS gaming.
Though note that there are several keyboards with split layouts + tenting (the two most important aspects for relief) that cost a fraction of the Adv 360; $200-300 of the price tag is for features, build quality, it being pre-built, and ease of programmability.
It is, even in the USA, $129, compared to the $20 or so I'd otherwise expect to pay when buying a computer for a new employee.
Here in Denmark the RRP is 1699DKK = $267 = €227. (Still $215 without the VAT.)