So that would bring his take-home from the deal to between $430 million and $670 million. That's unless he somehow shielded his stake with trusts or offshore entities, which is possible.
But if it's a straight sale with typical tax treatment, Dr. Dre would need additional assets of between $330 million and $570 million in order for the Apple deal to make him a billionaire.
That said, Dre is the greatest wealth creator in the history of hip-hop. And is there really any difference between having a net worth of $700 million or $1 billion? Either way, it's enough to buy most of what anyone could ever want.
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And if he says he's a billionaire, he would certainly know. But contrary to his video statement, Forbes will not be updating its billionaire list. O'Malley is saying Dr. Dre is worth closer to $800 million.
And indeed, my own math suggests that Dr. Dre would need to have significant non-Beats wealth (at least $300 million) to get him to the 10-figure club.
—By CNBC's Robert Frank.