Here's what I've found over the past few years. On games where you would think you could pick tix up off the ground, you won't find a soul selling them. On big games, just bring a little cash and get all you want. My buddy and I carried 4 into the USCe game. There must have been a hundred people selling tix right outside the gate and NO takers. We were standing there hollering FREE.
Conversely, my in-laws came in for the Arky State game and we needed 4 together. I eventually went up to the ticket office and paid face value for em' because there wasn't a soul selling tix outside the stadium. I went to the Furman game last year thinking I'd just pick one up. I found one tic for sale just after kickoff.