Why the hell do they need 1 billion?
Why is everyone so obsessed about it?? This article says that 4 of the previous films didn't get to 1 billion as if it was something bad, well this is a one time gamble, if this was actual bad news, the DCEU wouldn't have gone past Man Of Steel: https://www.cnbc.com/2017/11/17/justice-league-faces-a-steep-climb-to-1-billion.html
Also:
No, a movie's cost is not twice its budget
No, advertising for a movie doesn't cost 100 million.
No, revenue doesn't decline week to week.
Get over it.