WWE released their Key Performance Indicators for August at this link. According to the report, WWE averaged 245,000 worldwide pay-per-view buys for July and August. With July's Money In The Bank pay-per-view estimated at 192,000 buys, that would put this year's SummerSlam at 298,000 buys. The show was headlined by John Cena defending the WWE Championship against Daniel Bryan with Triple H as special referee, while CM Punk vs. Brock Lesnar served as the semi-main event.
That is a steep 17% drop from last year's SummerSlam, which initially garnered an estimated 350,000 PPV buys. Last year's event was headlined by Triple H vs. Brock Lesnar.