I just looked at the ESPN website, and they are calling 850 000 a "whopping success". I don't think they were ever actually expecting 1.5 million. I'm not sure where that rumour came from. They are saying that 850 000 makes this the biggest non-heavyweight fight ever that doesn't involve De La Hoya.
Fightnews.com and everywhere else is also reporting this as being a big success. I really just think that 1.5 million expectation was just a false rumour going around on this site that everyone latched on to, which can definately happen.
http://sports.espn.go.com/sports/boxing/news/story?id=3158134
This indicates that 850 000 may have been even higher than expected by the sounds of it.