General Admission tickets, which cost $337.50 for all four days plus camping, are currently sold out, but you aren't entirely out of luck. There are still plenty of Platinum Tickets available which, considering how much more you get, are a bargain at $575.
The VIP tickets also include 4-day entry to the festival, plus access to VIP viewing areas at all four stages and the dance tent, access to the Sasquatch Superticket Hospitality Area for all 4 days with complimentary food, beer & wine, soft drinks & bottled water, access to the Cliff House (a private club near the main stage with air conditioned private restrooms, a cash bar, special menu and the best view in the venue of the Columbia River Gorge), and merchandise credits. The private bathrooms alone are worth the additional $238.
Platinum Tickets can be purchased via Live Nation, just don't wait too long since they are destined to sell out too.