What if he do not donate 75% of his Total wealth (around $ 750 mln)? Even if he donate $1 mln, that is more than any other individual who has given out in this crises. Remember Angelina Jolie pledged $100,000 (which was all over the news), and this is still higher than what our politicians gave personally.
And I do not believe that a person who has openly given this letter pledging 75% of wealth would not pay anything as aid. Even if he actually donates $1 mln in the end, he should be praised, rather than bombarded by unjustified criticism/doubts, as can be seen in many posts above.