It's a priority of the project is preserving free tailgating and student access. The "premium" area makes up a fraction of the overall space and the proceeds are intended to pay for maintenance so the grounds don't deteriorate.
Overall the net land area increases because the spoils from the lake carve are used to level off other areas that aren't usable today.
Bear in mind - tailgating may be important to a lot of folks here, but it only happens 6 days a year. The whole rest of the year this is a student venue and one of the first things prospective students, recruits and other visitors to campus see.