WWE has released the preliminary buyrate for the Extreme Rules PPV back on 5/19/13. The early estimate has the show drawing 228,000 buys as of 6/24/13. In comparison, the show in 2012 drew 263,000 buys, 209,000 buys in 2011 and 182,000 in 2010.
WWE will release the final buyrate in the second quarter financial earnings report.
Source: WWE Key Performance Indicators