That means, Paul McCartney, Beyonce, KISS, Prince, and the Red Hot Chili Peppers all performed without getting paid. Here's how it works:

The NFL doesn't tell them what they can and can't play. They can put together their strongest material, even if it isn't theirs like Prince did. The NFL pays for all promotion of the show and any other ads, like stand-ups for grocery stores, or other promotional material. The NFL does give them money for production though. You can hire any guest musicians, dancers, lighting show, pay for hotels, food, etc. This runs into millions of dollars. So, you have the promotion, the world's biggest stage, and money to put on the show you want.

You as the musician, will not be paid. Not one person has complained about that of the ones that have performed. Everyone that has been asked to perform is told that right off the bat. Would you do it for those terms, me? Yes!