Seriously? It's right there on the Tickets & Camping page of the official website.
"Beginning Monday 2/14/11 at 10am: FOUR DAY passes increase to $295, single day tickets to any four days will be available for $79.50 (again, all prices all inclusive). These prices run (if still available) until midnight May 26th.
Beginning Friday May 27, single day ticket price goes to $89.50 for each day (no more 4 day passes available). Again, price is all inclusive."