All my state, local and federal taxes (including SS deductions) add up to about 33% of my paycheck. Even though I'm a government elite and all, I only make about $52,000 a year.
That 14% added up to several million dollars in taxes, not to mention a greater sum in the form of charitable donations. He apparently gave about 30% of his income to charity, as opposed to 5% for the Obamas and .1% for Biden. Of course, Obama is very generous with the tax money that he got from Romney, but that's another issue.