I think the obstacles to practical, competitive fusion power, particularly DT fusion, and especially the mainstream approach of JET/ITER, are so great that calling investment in it "the economic equivalent of perpetual motion" is not far off.

Good thing I didn't compare fusion to perpetual motion, then. I was pointing out that his too-simple approach could be easily misapplied, and picked an especially obvious negative example to counter his especially obvious positive one.

At this point we just don't know whether fusion is like airplanes or whether it's like perpetual motion. Unless you are proposing building an actual star, the existence of stars tells us approximately nothing about whether a fusion-based power plant is economically achievable in our lifetimes.

I think it's an interesting idea and I'd love to see it happen. But I think it's important to be realistic in our discussion of it.

The "stars exist!" argument really annoys me. Among other objections, stars don't even use the specific fusion reactions that terrestrial fusion reactors would use.

Stars are, anyway, not subject to economics. It is the combination of Tokamak fusion power generation with economic viability that resembles perpetual motion.