ITER: World's largest nuclear fusion project begins assembly

However there's also just the actual literal cost of RnD. There's no hard cost in budget either.

It's more like an apples to oranges comparison, but look at the progress that SpaceX has made in commercial space flight, and that's AFTER we've established that it's possible with all of the path-finding missions in the half century prior.

Fundamental research is an investment in the future. Aside from ensuring that the basic levels of Maslow’s hierarchy of needs (1) are met, funding research that expands the public infrastructure and public domain of knowledge of how the world works, and third designs for common industrial infrastructure, such as power generation.

Commercial fusion would be either much closer to reality or known to be infeasible with current technology if research were funded both adequately and predictably (so people could make careers and lives in that).

(1): https://en.wikipedia.org/wiki/Maslow%27s_hierarchy_of_needs

Is it due to precision requirements being difficult to achieve? Supply chain delays for custom parts? Lots of experimental runs that require dis-assembly and tuning?

The problem with statements like this is that when they're proven wrong (they aren't always, but when they are), it's often because of some massive underlying shift that makes a bunch of assumptions wrong, leading to a wrong prediction.

If we envision a system where not only delivery, but storage is centrally managed, then yes, there's a massive amount of energy storage required, and that's hard to justify and invest in for large companies.

If instead you assume that maybe electric cars will act like large battery reservoirs, and stuff like the powerwall will also be used to supplement it, then we end up with a massive amount of battery storage already distributed to different endpoints, an d paid for by individuals instead of a few massive companies.

Whether that's all that likely, or even possible at a huge scale because of required rare materials is a question, but that's an entirely different type of scenario than "energy companies invest in massive batteries to leverage solar/wind for efficiently", and the type of thing that's hard to predict and because of that often overlooked. That doesn't mean stuff like that doesn't happen all the time. In fact, I would say there's a major shift like that every decade or so, we just don't necessarily notice them unless we look at them.

The internet itself was a major thing. Just relating to the internet, there have been major advanced every few years. The rollout of new major advancements is unevenly distributed and often over the span of a decade, leading to it being hard to notice them. Just this last year, the massive increase in remote work will likely cause a major shift in the economics of many markets, and change how many predictions would play out.

Bringing this back to energy, consider that it seems like every year California is having massive fires, and is bankrupting its public utility provider to the point that the state is prepared to take it over if it gets much worse. At that point, if the state decides it needs to actually replace a lot of infrastructure that PG&E needs to maintain, maybe pushing for some partially distributed model starts to make sense.

These are all things that go into making predictions about energy really hard, since we're at an inflection point where a lot of stuff that used to work is not working very well, and new technologies are just at the cusp of being useful.

6 months of people staying at home are causing economic crisis.

Large cities literally depend on cheap energy to survive, to bring in food and move away the trash. If there is no power for a week, London and every other megacity turns into a mass graveyard