I guess I’m a bit late to this thread, but as an engineer who’s been doing custom work for a few decades now, I don’t think it’s over-engineered. It’s well built, and doesn’t seem to have planned obsolescence built in. Sure you could go and have a bunch of sheet metal parts that slide on bits of plastic that will wear out in 2 years. You would save a few bucks. You could go and save some money on casting parts instead of CNC — if you were planning on having a production run large enough to justify the costs in tooling. Otherwise CNC is a perfectly fine way of going.
The gearbox probably does cost 35-ish dollars. A bunch of molded gears would be half that. And would last 1/2 as long under regular use.
It seems that the designers just wanted to make something that was quality and could be ‘passed down to the grandkids’ instead of “optimizing for cost” and making what I would call a cheap piece of crap.
Mind you the concept for the product is amazingly silly and I cannot see any reason for it’s existence (outside of maybe being some sort of huge conceptual art piece) but at least they built it with quality in mind, and whoever did the work can take pride in what they did.