The biggest delays for ITER were all political in deciding where it would be built and who would contribute what. Yes, there’s been some technical delays since then, but compared to other projects of this scale it has actually gone fairly well.

The DEMO units to follow ITER should be able to be built by individual nations. Those should got a lot faster and hence cheaper. The whole point of structuring ITER the way they did was to give all the contributing countries experience in every critical system. That’s very inefficient for this particular project, but should make follow up projects a lot more feasible.