The bulk of it is the custom keycaps (a keycap run is seriously expensive, especially if you're using weird key sizes), the enclosure, and the switches. They're probably being hosed by their suppliers too, since I can't imagine they have the money to invest in serious volume.
That said the board looks seriously under-engineered. It's a bit ridiculous to invest so much in high quality switches and an enclosure built like a tank without spending any time on designing the board to withstand any forces, passing the buck onto their customers to make sure everything is soldered correctly...
I'd be confident the enclosure survives a fall and lasts a lifetime but certainly not anything inside it.
I think you and I have different bars for what “expensive” means.
Manufacturing things is expensive because of the fixed costs. To make it cheaper you need to make enough sets to dilute the fixed cost among N buyers. If at N=20 the price is already something people will pay, that’s not expensive IMO.
The problem is that the case doesn’t work that way, because the costs of machined aluminium are pretty much linear with N.
