I think Ledger's death had very little - if anything - to do with the movie's BO success. How many people said "I have to see TDK to pay tribute to Heath"? Few, if any, I'd say.
TDK is a big hit because it's good and people like it.
Oh, and if this LaSalle guy isn't yanking chains, he's a grade-A jerk. He wins bets (in his head) because he weasels out of them - classy! :rolleyes
I think Ledgers death was huge in making it a box office success. Before he died, I never heard the phrase "Hey, Heath has a new film out, let's go check it out!". When he died, a good 60% of the status messages on my facebook (and I only average about 150 friends on it) where about him, from people who I never knew to even be into movies, period, much less comic nerd ones (I'm including myself in that nerd group by the way...). All the reports practically listed the role of the Joker as a cause of death. As such, seeing this film became the movie equivalent of buying an Iphone on the day of release, hence you had the line ups and pre-sales. Yeah, it being a Batman movie helped, but Ledger dying was huge in the anticipation. The bonus is that it's apparantly a good movie. I haven't seen it yet since I hate crowds and people (see number of facebook friends...)
It made a bit of difference, but Heath Ledger's last film is still coming out. That's not going to do $400 million+ or probably even $120 million+.
And then again, if they really were that obsessed with box office they could have cast Johnny Depp or Leonardo DiCaprio as the Joker (keeping the script and everything else exactly the same) in the first place and still have achieved the same results IMO.
The film is also showing very good legs, like Batman Begins. So maybe the Ledger thing contributed to a strong opening weekend, but to be crushing records left and right two weeks later? The movie has to be hitting a nerve with the audience and drawing strong repeat business. Lets just face it, I think the more "serious" take that Nolan has taken attracts people like women and older people who normally wouldn't really give two hoots about characters that dress up as superheroes.
The Nolan films still work as crime films, and in TDK's case, works as a thriller flick. And also looking at Friday's box office -- so much for The Mummy "crushing" TDK, looks like another close weekend especially if word of mouth spreads quickly on how bad the new Mummy film is.
I read an article speculating that Titanic numbers may be possible for TDK. I don't know if that's true or not, but I don't think I'll ask Charles to pick any lottery numbers for me.