I don't believe you need to prepay for a parking pass. There are more than enough parking areas very close to the stadium in Tampa to accomodate the crowd. Three suggestions.
1. To the west of the stadium, beyond Hillsborough Community College. Nearly everybody in this neighborhood turns their yards in to parking lots on game days. This will be the least expensive area to park. However, because they are trying to get as many cars in as possible, that will leave you needing to find somewhere else to tailgate.
2. To the east of the stadium there are several lots very close that you can park in and tailgate in. These usually run about half the price of the 'official' lots.
3. There is a mall about two miles away, International Plaza. Park there and pre-game at the sports bar there, Champs. Then take a cab to the game. The cost of the bar tab and cab fare could end up less than the cost of an official parking pass.