According to numerous sources, the price tag for Men in Black III is around $375 million for all facets of this film (production, marketing, distribution) which is actually $25 million above the costs that Disney incurred to bring The Avengers to the big screen.
Why did it cost so much? Well, apparently the studio had to grab Will Smith while he was available so they actually began production before the script was even finished. As anyone can tell you, that often translates into a bloated production budget, and given the obligatory $100 million marketing campaign, that implies a production cost of at least $230 million which is inclusive of actor salaries, various rewrites, etc.
Now that the money is gone, the focus has turned to whether or not Sony could actually recoup their investment. All early signs point to yes. While the second installment in the saga shrank from $590 to $440 million globally, pent up demand for a Will Smith-lead blockbuster coupled with a shot at franchise redemption is expected to drive this movie to box office glory. Early projections have Men in Black III opening up to $80+ million in its first weekend which would mark a best for the 15-year-old franchise.
Of course, such a debut would barely make a dent despite its impressive nature. Audience reaction will likely dictate whether the movie does indeed make a profit as it will require a lot of repeat business amidst heavy box office competition in the weeks that follow.