The idea that a movie's published production budget has anything to do with what that film cost in reality is simply just laughable.
The studios typically provide a budget figure to the media. That budget may or may not reflect reality. If anything the studios lowball. But the reported budget figure can be used to broadly establish how successful a film is and it can be used for purposes of figuring out whether a film has a shot at a sequel. If the worldwide gross isn't at least double the reported production budget then a direct sequel almost certainly isn't going to happen. I can only think of two films that got direct sequels despite grossing less than their reported production budgets, both Paramount releases: Star Trek: Insurrection
and G.I. Joe: The Rise of Cobra
, and the latter was made on a reduced budget and with significant cast changes.
An outside observer obviously doesn't know the granular details of any given movie's financial position, but there's enough coverage from journalists and financial analysts that the ecomomics of the movie industry aren't a complete mystery.