simple, whomever designed it, didn't share the design. They made X # of them, and now they don't make them. Yet there are still those who want it.
I saw this pop up right away, and I would have loved to get it primarily for bench testing vectors.... but hard to justify $500 for one of these, as in most cases you can get a genuine vector monitor for at least the same or less. So, I couldn't justify $500 for a bench tool when I could just use a genuine vector monitor. Once I get a good o-scope with x-y mode I won't need either.
I use an old NEC (I think the last model before they splattered them with "multi-sync" labelling) which will sync to 15Khz... IIRC it can handle 800x600 tops, so this would have allowed me to use the same screen for benching.
It would be great if they would make them again, or someone else would. Might be even nicer to support a higher pixel density than 800x600. I'd like one, but @ $500 it won't be happening any time soon.