Here is the run down from the past couple years of the PPV buy rates & the main events:
-2012 Extreme Rules: John Cena vs. Brock Lesnar did 263,000 buys.
-2011 Extreme Rules: Steel Cage Match: John Cena Vs. John Morrison Vs. The Miz (c) did 209,000 buys.
-2010 Extreme Rules: Last Man Standing: John Cena (c) Vs. Batista did 182,000 buys.