Well there's no guarantee that it's half (unless you know more about this from a day-to-day level). Auto industry: some can get 25%, others get 75%. The more the payout, the more "editiorial control." This would be things like the PS3 chime must be in the ad, and take up 1 second of the commercial, as well as show the PS family logo.
Also, with Madden, they made two sets of commercials, one touting XBox Live, and the other general ad for PS2. Again, old hat, but those new to this system wars thing gotta have something to say.