They could easily get an E2 entrepreneur visa, and the necessary cash is as little as $300k, most of which can be withdrawn later, so it's effectively a free citizenship as long as you have cash.
You probably will be able to soon though, and it 'only' costs $5m: "A ‘Trump Card Visa’ Is Already Showing Up in Immigration Forms" [0]
I couldn't blame you for not having seen this though. It was quickly flagged and never whitelisted; like so, so many other important stories here this past few months. Check my favorites for more falsely flagged stories.