WWE has updated their Key Performance Indicators through January 31, 2013. In them, the preliminary buyrate for Royal Rumble 2013 featuring CM Punk vs. The Rock for the WWE title is reported.
The show did an estimated total of 443,000 buys or right around last year's number. The show did 443,000 buys in 2012 and 446,000 in 2011.
While the final number weren't be released until quarter one earnings for 2013 are reported, you can view how the estimate is graphed with more data here on WrestlingNews.net.