If you have half a million dollars in free cash you can afford to set aside for a few years (you'll even get most of it back), you can buy a green card.

Yeah that's not most people.

That being said, the green card lottery is apparently much easier if you're from Europe (because of the lack of competition for the 7% country limit of cards).

But overall, the US is among the hardest places in the developed world to get a good visa situation, I think.

Yes, actually. I have also directly seen people with high levels of wealth get one in < 24 months (perhaps even 18).

And how many of these people had previously renounced US citizenship?