Which factors in marketing expenses (not included in the budget) and the fact that studios only receive a portion of ticket sales. The general rule would tell you that break even is $750m box office gross.
However, the general rule is just that, a general rule. The numbers are even worse if a movie’s box office split is internationally heavy.
Anyway, $800m was just an example to show how much you need to gross with that size budget. I have no idea what this movie is tracking for. They’d clearly be ecstatic with $800m, that’s a box office smash hit. For all I know this movie could be tracking for $250m.