If original keyboards are going for such high prices, perhaps it would be worth doing as another replica project? One of the varieties of Cherry keyswitches may be close enough in feel, and making a PCB with the correct layout wouldn't be difficult. Might need to get some custom keycaps printed for at least a few of the keys though.
I am off-and-on working on adapting an existing Chinese mechanical keyboard PCB to work on an Amiga as well as USB, since the "big box" Amiga keyboard parts are becoming rare and so expensive that it's cheaper to build a whole new one.
I don't think I have the knowledge quite yet to design a keyboard PCB, and my IIe works okay except for two switches (which I just ordered for $5/10pc + shipping). In ten years, though?
It would be really cool if someone made a replacement PCB that still fit into the II/II+/IIe case but with Cherry switch spacing.
Then you could build your own - they're pretty common and there are even some cheap "compatible" options (Gaterons) that have the same footprint out there.
The Cherry stems won't fit the Apple IIe keys as far as I know, however. Wouldn't be quite the same without the same key caps, although I'm sure someone in the mechanical keyboard nerd world could get replicas made.