It's almost impossible for a band that has as large of a fanbase as Pearl Jam to tour without using Ticketmaster. If anyone remembers their 1996 tour when they used another ticket source, it was almost a disastor. They had to play a smaller venues so many of their fans couldn't get a ticket. Also, there was a big issue with someone in the ticketing company who stole the credit card information of the concert goers. I remember getting my statement a month after their concert to see someone had bought gas and McDonald's somewhere in Pennsylvania.
Stuff like that rarely or never happens with Ticketmaster.
Like Arya said, you can buy tickets cheaper through the Ten Club except I think you have to be a member for over a year to get tickets.
This year, ticket prices are VERY high. At the Coral Sky Amphitheatre in West Palm Beach, tickets are running from $38-42 without all the service charges! I went to their concert at Coral Sky in 1998 and the ticket was only $26 without the charges. That's a huge price difference.