The show looks to have done between the 1.06 million buys that UFC 66 did in Dec. 2006 (Chuck Liddell vs. Tito Ortiz II) and the 775,000 buys UFC 61 did (Ken Shamrock v. Tito Ortiz II).
The number for the heavyweight title fight may not live up to the UFC's billing as the biggest fight in history in terms of numbers, but certainly means windfall coin for all involved.