The relatives were involved in the production.
How is using the actual places and people "cheap"? It would have been easier to get generic sets and fill them with extras yelling dramatic lines. As evidenced in his film "Bloody Sunday", director Paul Greengrass is deeply committed to the truth. He did everything to ensure the film would be as realistic as a movie on this subject could possibly be.
From what I've seen of Oliver Stone's film, it looks like he's taking the easy way and making a standard Hollywood movie about "courage and heroism" (and possibly "love and friendship"). It may use a real tragedy like 9/11 as the context for its plot, but the characters themselves barely resemble human beings. I can't say I'm surprised to find that walking clichés move you more than real people, though...
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