ITER isn't a EU but international project and was never meant to be cheap: If you want something to be cheap you don't ask ten different companies in ten different countries to produce one coil each.

Doing it that way was a political decision, it's about technology transfer, building knowledge in different countries, not building a cost-efficient reactor.

You can build more complex stuff much cheaper, e.g. the Wendelstein 7x project costs 1.3bn, and that's including all wages for the general Max Plank outpost in Greifswald for 18 years. The reactor itself did cost 370m. It's way smaller than ITER, yes, but have a look at the Lovecraftian geometry and you see why it's just a tad harder to build.

This effect is present not only in infrastructure projects, but all other type of projects, including personal ones. Any project that involves doing something completely new (to you or in general) will most likely take more time than, initially estimated.

With a project like that it's simply impossible to estimate how long it's going to take and what is going to cost because you don't really have a clear idea of what you're going to do in the first place.