Let’s suppose this proposal works out, ITER will become a very expensive boondoggle. A technological dead end. But if you’d taken the ‘Manhattan Project’ approach and thrown 10x as much money at fusion research 20 years ago we’d most likely have spent most of it on a super-ITER. It might be operational by now and might even have reached break-even on power generation, but in the longer term would now be just as redundant and superseded by this new approach.
Eventually there is a break even point (for the closest solar systems, last I checked, it's around 400 years), but in order to know what it is you need to know the amount of time to reach the goal and your rate of increase. I don't know if there's a way to estimate that with fusion research.
Obviously people are free to choose differently and there are exceptions, unique circumstances etc.
And in fact, it looks like Sparc is more of an exercise in making fusion reactors cheaper, most notably by using different magnets. ITER is more about validating the concepts, with no regard for the price. Besides the fusion itself, ITER will study how to inject fuel and evacuate the waste products as it is running. They will also tackle the problem of producing the large quantities of tritium a fusion plant requires.
So, my understanding is that Sparc is not intended to make ITER obsolete, but instead tackle a different problem. If commercial fusion reactors happen one day, I expect they will have a bit of both.
Or maybe someone would have had enough sense to think "you know, what we really need is better superconducting magnets. Let's throw 1% of the budget at that problem."
The problem is (1) the earlier you spend big the greater the chance you’ll pick wrong because you have less information to base a decision on and (2) Spending big doesn’t actually improve the odds that the approach you pick will end up being the right one. It just means you find out sooner.
The GDP of the EU is apparently $18 trillion, so $20 billion is about .1% of the GDP in a single year, and of course that $20 billion is spread over 1-2 decades. If anything, it seems like as a species, we should have more of these bets going. What if we spent 1% of our GDP on 10 long-shot, high-impact projects? Or hell, half a percent on 5 long-shot projects, and half a percent on solving the dozens of problems that we could solve simply by funding them.
And this approach will be superceded by something else. And that will be superceded in turn. Should we wait forever? We'd still live in caves.
These new approaches don't just show up, they come from the knowledge and scientists trained in whatever the previous approaches were.
Lastly, if this approach results in having cheaper fusion power, but needs extra 20 years of R&D, thats time we don't have.
