Energy recovery was already doable with traditional actuators through BEMF generation, so the only thing this has going for it is static torque.
The only way i'm seeing this doing things at a fraction of the cost is by enabling the use of a smaller motor and repeatedly winding each spring before doing a task requiring more effort. At that point, why not just use a linear motor and even more clutches to do that winding instead of having to move the entire arm?
The premise thrown to those economists is slightly different - that AI is more productive than a human at everything, but not necessarily cheaper, then sends their different interpretations, which i've ended up summarizing as:
Noah Smith: Compute will remain limited, so it'll be directed at whatever is most profitable.
David Autor: AI can make the big-bucks jobs available to everyone, but they still need to Git Gud and figure out how to harness AI for them... Until everyone does. Pray "everyone" gets small enough by then so there will still be enough bucks left to live.
Daron Acemoğlu: Rest easy. AI won't cover everyone's jobs any time soon. Things will still suck when it does, though.
Ethan Mollick: AI won't cover all jobs, but it's about to cover all the "good" jobs. I don't want to think what happens next.
Noah Smith on the earlier comments: Society will hopefully sort itself out and still leave humans "some" role. Relax.
Pascual Restrepo: You'll still have "some" role, buuut it will become irrelevant anyway as AI will play a colossally larger role in the overall economy. Pray AI's profits get distributed to everyone.
I think all of this misses the point completely. Compute can still be limited, but i think it's more likely to happen through the supply-demand curve. Even if it remains expensive forever, there will likely be a point where the value of AI will equal its compute cost - once that is reached all AI jobs pay the same per compute time AI spends on them. Under the comparative advantage umbrella, the best-paying jobs for a human would turn out to be the jobs AI is the most inefficient at relative to the human regardless of whether they're fullfilling to the human or not. but this still misses a much bigger problem.
Production needed land, labor, and starting from a certain technology level, capital. There used to be a social balance here in that everyone had their own labor and society always managed to figure out the price they'd sell their labor for - even if that price was different over time and over different societies, they'd still manage to sell it anyway because there was someone willing to buy it in the first place.
With AI, capital can now become labor instead of only amplifying production per labor. The industrial revolution was merely an inflection point where the amplifying factor of capital made labor without an amount of capital out of reach for most individuals uncompetitive. The ARA revolution is merely an inflection point where capital is making human labor uncompetitive.
On old societies, everyone had access to enough land to survive(or thrive) on their own labor with a capital multiplier small enough to be achievable by oneself - you could sell the labor to yourself and get a more enjoyable life in exchange. As societies got larger, the land available per individual got smaller, but capital could still allow for success. People with large amounts of land/capital figured out they could get more by lending their land/capital to others in exchange for labor, and society could figure out the exchange rate for which they were willing to trade those because labor was scarce.
ARA is bringing a post-scarcity economy, but the post-scarcity is coming to labor first, society has grown large enough that there's not enough land for everyone to survive under their own labor without access to capital, and the people with land/capital now have enough that they don't need to buy labor anymore. Worst of all, they're now worse off by letting others labor with their resources for free, because the cost to keep them alive is now higher than the benefit their labor would bring to them. Society doesn't like this, but what can it do about it?
tl;dr: George was almost right.