Those who can afford it and have a use for it will buy it. The rest of us will (mostly) think "that's nice" and move along. As I posted above, it's a limited market. That said, Hitchcocks' managed to sell all their reproduction Big Head kits for Redditch and Indian 500 iron barrel Bullets despite the price, Baxter Cycle even bought up the reject castings to fix them. I would assume a company like Hitchcocks' would have researched their likely market carefully before taking these beyond the back of envelope sketch/drawing board/CAD file, or whatever voodoo modern manufacturing currently uses. My suspicion is that they'll sell most of them once the all the money from the sale of spare kidneys has been banked.
If we're talking about investment, I think there are enough level-headed people in the RE world who realise that any major upgrades made to their bikes won't necessarily be recovered when they sell their bikes on, Same as restoring a vintage bike, the money spent on a really good restoration isn't often recovered in a subsequent sale. However, people do gain a lot of personal satisfaction seeing an old heap of a bike restored into something desirable again, or taking an under-developed production bike and turning it into something a bit special. If you don't get that, others here certainly do, and no, I haven't ordered one of these kits, for sure/shure.
A.