I purchased a parking pass in the yellow lot (across the street) for the $10 at the official UM site two days ago. Might be too late today. Another option for a discount is to pay with your sunpass account (you must activate the parking option ahead of time) that will be $15.00. If not go to the yellow parking lot tomorrow and it will be $20 cash. I saved $10.00 by pre-planning a bit.
Still can't edit posts on here. They might stop selling them the day before. Yesterday I got an info email and it said to buy parking passes yesterday for a discount. There are no game day sales in the interior lots.