The cost of making one it probably several thousand dollars, not counting the year and a half of Bunnie's time.

From then on it depends on how many you want, and if you can find an assembly house that will take a tiny order for (say) 1000 of them. Even in large runs I can't see it costing less than $1000, partly due to the FPGA on the board. Handcrafted aluminium and leather cases are also likely make up several hundred dollars of the price. That case looks particularly resistant to mass-production.

I tried doing this as well, about a year and a half ago. I gave up relative early in the process, though, as I had hit the upper limit of my electronic design skills, and figured I'd better wait a wee bit more until they would either be on-par with the difficulty of the task, or a good-enough SBC shows up. Based on that experience, I'd venture thinking the price is in the 1000 USD range, with the costs of actually producing the boards (alleviated by more or less preferential access to the required tools) being a significant drag.

That being said, I think it's worth it. I can't think of a single laptop which I'd actually love to use forever, or at least until it's so old that it becomes utterly unusable. The only thing that prevents me from declaring this one as the one I'd like is that OpenBSD is a bit shaky on that architecture IIRC.

If I recall correctly, bunnie's laptop was in the $2.5k range? I could be wrong, but I remember it being very high compared to mass-produced things, which makes perfect sense.