My understanding (please correct me if I am wrong) is that he will be able to put on his tax return, in the next year or two that he has given these shares away to charity. However, the IRS don't calculate his splendiferousness based on the price at the time they were given away, but at the time they do the calculations.
So if he gives them away today at $27, but when he declares the gift (in say 2 years time), the IRS will take the price then (for example $35) and then he gets tax relief based upon that figure. So instead of 30 million at $27 = $810 million, he will be allowed to claim 30 million at $35 = $1,050 million as a donation. He gets 240 million extra allowance.
That will buy a few drinks for Christmas!