I'd finally feel financially secure

Really?

If anything less than $1B isn't enough then it is never enough. $1B is the new $100M thanks to ongoing currency debasement.

Also, there is something called "taxes" which is what makes anyone who has millions or billions to want even more money and the IRS will still come after you anywhere in the world.

Otherwise they have to renounce their citizenship and move to a tax haven.