The problem is, that isn't about "netting more money" - when you lose season ticket holders, you lose affiliation with the U. Season ticket holders start out as buying single game tickets, then they skip a single game or two to do other things in the Fall, they justify missing a non-conference game or Purdue, and before you know it, these season ticket holders realize they are "OK" only going to 2-3 games a year instead of 7. This turns them into a casual fan. Multiply this over a few thousand and its dramatic.
It's a lot easier to maintain a season ticket holder than it is to acquire new ones.
Go Gophers!!