Giving away $500 Million is giving away $500 Million. The charity is receiving $500 million. Zuck doesn't get anything for it at all. If he earnt so much that h

Giving away $500 Million is giving away $500 Million. The charity is receiving $500 million. Zuck doesn't get anything for it at all. If he earnt so much that he was able to write off $500 million, that just means he pays less tax on the rest. But at 30% tax rate, and if the whole lot was deductible (it wouldn't be), it's still $350 million out of his pocket. He's not benefiting (financially) in any way.