My definition of "wealthy" is a person who doesn't need any income. They can do whatever they want realistically for the rest of their life with zero percent income. And, if they did that they would pay no income taxes.
Many/most wealthy folks have their money mostly tied up in assets, say they started some company or whatever. If they don't sell any part of that company, they have no income (unless it pays a dividend, and that is taxed favorably). A wealthy person doesn't need to "hide" his money, he just needs to avoid having a bunch of income, and even if he does, he keeps most of it anyway, and still has his wealthy.