EU structuran development funds are ~34 billion a year for all of EU. Unemployment and other benefits in UK alone are 200 billion.
the amount of fiscal transfer that happens withing any nation is huge: all the unemployment benefits, infrastructure spending, salaries of government employees working in poor areas, etc.
Conversely, I have seen successful implementation of multi-billion euro projects.
Why can Germany invest money so much better than half of Europe? Same for Nordic countries.
I've been thinking about it a lot. It has to be culture. Germans in the government actually care about their own country and countrymen. They still line up their own pockets, mind you, but not as bad as Eastern Europe, for example.
And mental healthcare in Germany is absolute garbage, by the way. Which is pretty weird considering how much they invest into it.
But again, culture. You're suicidal - you're weak. You don't have ADHD, you're just lazy. Homeopathy is real. Vaccines are dangerous. Etc.
For an even better example, see India where the poorer states get very large subsidies and investments and quite a few have had substantial quality of life improvements over the years. People argue that Europe can't have a union because of its diversity but India is far more diverse in terms of languages, culture, religion and politics and has still managed to forge a nation atate.
In Europe, the rich countries essentially keep their own taxes and don't transfer and invest taxes in the poorer ones, so being tied to a strong currency trips up the poorer states badly - all the disadvantages of being a weaker area tied to a strong currency without any mitigation factors beyond the right to move away.