...the next pick to the people who saw you pick the "winner". Now half of those people see one team, the other half see you pick the other team, and whoever saw you pick the winner thinks you've got a 100% accuracy rate over two games. You could do that for a while and then offer to sell your pick for the Superbowl. Starting with a big enough group in the beginning, this might be really lucrative.
But is it legal?
Deception is tricking people into paying or paying more for a service by lying. And I’m pretty sure a lawyer could say that that is lying UNLESS you never mentioned your last picks and how you have good choices. Just say I’m not giving my prediction for Super Bowl unless you pay $5