The credit for the jump (up from 301,000 buys last year) has to go to the lure of Brock Lesnar vs. Triple H, which featured the return of Paul Heyman and Stephanie McMahon, as well as several storyline injury angles. Obviously, the audience bought into the storyline.
As noted, the CM Punk vs. John Cena WWE title unification PPV drew 301,000. The 2010 edition of the PPV drew 350,000 with The Nexus vs. Team John Cena. The 2009 edition garnered 369,00 buys.