$400m is supposedly going to the actors, director, writers, producers, etc... Which is good because I assume some of those actors are getting a raise but considering the first two Avengers films were sub-$250m and Disney kind of sees AoU as a disappointment for making less than A1, I'd imagine they'd expect IW to make $1.8b-$2b each? Well maybe for the second one since the conclusion will likely get more viewers but either way those are very, VERY tall orders.
$3bil each? No way. Combined, easily.
Once kids see Spidey web slinging with Rocket on his back holding a big *** gun, Hulk & Groot, Iron Man in space with the rest of the Avengers and GotG it's over.
I mean pt. 1 is almost guaranteed for that and for pt. 2 not to reach that the movie would have to be really bad. You know they ending Pt. 1 on a cliffhanger to bring everybody back.