Try some algebra on the following statement(solving for effective tax rate before and after. There are two unknowns and two expressions):
under Romney’s proposal, people with $1 million or more in annual cash income will receive an average tax cut of $250,535. Those in the millionaire category will receive an 11.8 percent increase in after-tax income
To get $250,000 in savings, you have to made a heck of a lot more then 1Mil.