That's Al's move, he did it with Beverly D'Angelo too. Years ago, he did an interview were he admitted he had a bad relationship with his own father due to him not being there, so he vowed to never let that happen with his own kids. So, he doesn't mind paying big child support, but he makes sure he gets what he wants in the agreement.
A few years ago, he was paying around $500k/yr for his twins, they're predicting a similar number for this single child now. Not huge money for someone like Pacino. He's happy, she'll be happy, etc.....