Just thought I'd comment to link this from the article in case anybody misses it:
When I wrote the article, I believed it was still produced by the original company. I later learned that while the same company produced the RB5X for about 20 years after its initial release, eventually the name & the remaining stock was sold off, twice.
They kept afloat despite only having produced a handful of bots because the stock of parts was kept in somebody's garage & ever few years when an order came it, the gang got back together to build one.
If you've got an interest in these things & aren't confident about your ability to build one from scratch, the RB5X seems like a good choice: help them clean out their garage. If you are confident in your ability to build one from scratch, I recommend downloading the code, designs, & instructions for the Gemini from Mike Fowler's site -- the Gemini is more capable than even newer robots on the market at a price comparable to what they originally asked for, & the price of components can only have gone down since.
That strikes me as a tough price point to meet. Perhaps I'm jaded after having seen numerous 3-4-5 axis arms on thingiverse & hackaday being 3d-printed and built with servos & stepper motors for a couple hundred bucks or less.