> Fusion power is not a replacement for solar.
You're conflating ITER with fusion power in general. There're at least half a dozen competing approaches to fusion power with several orders of magnitude lower funding. Several of them are probably more promising than ITER, but ITER is primarily a political project, and only secondarily (at best) a physics project.
I am not conflating them. “Several of them are probably more promising than ITER”. Keyword: probably. There are no magic bullets. Would I be happier to see an optimized stellarator with a 10 meter major radius? Yes. A lot of the physics goals of ITER will apply to all MCF reactor designs. If you’re touting the benefits of non-MCF fusion: vaporware. I think many designs should be funded and explored, but it’s not like people haven’t tried clever ways to put particles together before.
None of them are particularly promising. They may be better than ITER, but that's damning with faint praise.
Fusion is a technology that's being pursued because it was being pursued, not because it's particularly attractive from a practical point of view.
As for breakeven: no plasma physicist I’ve talked to see it as some amazing barrier. It is what it’s always been: a publicity thing. It gets people excited so laypeople can point and say “See! It works!” without having to dive deep into physics and economics. The real physics goals of ITER are in testing models when pushed outside of previously measured parameters. You can’t just spend $50 billion on a reactor and hope it works. That’s why increasingly large and expensive science machines are necessary. Once a design is complete you don’t need diagnostics and scientists. You just need a tritium processing facility, some HTS coils, some vessels, and some plasma heaters.