CREATE TABLE table_35206 ("Date" TEXT, "Event" TEXT, "Location" TEXT, "Attendance" TEXT, "PPV Buyrate" TEXT)

On September 10 during Strikeforce: Heavyweight Grand Prix Semifinals, what was the PPV buyrate?
SELECT "PPV Buyrate" FROM table_35206 WHERE "Date" = 'september 10' AND "Event" = 'strikeforce: heavyweight grand prix semifinals'
SELECT "PPV Buyrate" FROM "table_35206" WHERE "Date" = 'september 10' AND "Event" = 'strikeforce: heavyweight grand prix semifinals'