ticket scalpers. They are now encouraging it through the deal with Vivid Seats. They are reaping what they sowed.
I held season tickets for the past 20 years. Dropped them this year. I was always terrified to sell tickets to anyone who might not actually go to the game, because ND supposedly was monitoring StubHub and other sites and busting ticket resellers. The threat was to cancel your season ticket subscription.
In hindsight, I wish I had scalped some, made some $$, and gotten kicked off the ticket rolls. Would have saved me lots of money and aggravation over the years!