I believe that it’s almost always wayyyyyyyy more expensive to CGI the thing. Sort of amazing to think about, but I think smashing up a bunch of cars, flying a bunch of helicopters, etc, is simply much cheaper than faking it with a convincing level of fidelity.
I doubt it's true in this case. Tom Cruise has done 100+ skydiving jumps, spent 6 months learning to fly a helicopter, and for the canyon battle they had to transport a crew of 150 people to the mountain and back every day using the helicopters.
No CGI is that expensive. I think they did it because of the craftsmanship, love for the art, perfectionism, stuff like that.
