As the title says, which big budget release for you was so expensive that you just can't fathom the idea that it cost that much... for a more streamlined conversation, movies with actual available budgets online (Pirates of the Caribbean 4, Avengers: Age of Ultron, Sahara) shouldn't be considered because you can actually see where did all the money go.
Some examples:
- A Sound of Thunder ($80,000,000): This one is quite obvious of you have seen this 2005 movie... if you're lucky enough for that, just imagine CGI with Scyfy quality, Ben Kingsley with a wig that even the 90s Power Rangers would consider fake and TV-like cinematography... and that's putting it lightly
- How Do You Know ($120,000,000): Apparently the budget for the cast (Jack Nicholson, Reese Witherspoon, Paul Rudd, Owen Wilson) and writer/director James L. Brooks was $50,000,000 I total and the film's opening and ending were reshooted... and yet that doesn't explain how production alone for a romantic comedy costed more than the entire budget for Deadpool.
- Unbreakable ($75,000,000): I know Shyamalan was fresh from the success of *The Sixth Sense at the time, so his writing few of 5 millions (plus whatever he got as a producer and director) is justified, and the casting of Bruce Willis and Samuel L. Jackson wasn't exactly cheap, but still the idea that a film with such a small scale filmed mostly in closed sets costing twice as much as the previous director's film is quite weird, specially if you think that his later film Signs (also another small scale film, but with a bigger star in Mel Gibson and some actual CGI) costed slightly less just two years later.
- Tangled ($260,000,000): I know the movie was heavily redone at one point and new technology had to be developed for Rapunzel's hair but even other troubled Disney animated productions didn't cost as much, and other CGI films with new developed technology also didn't reached such high budgets.
- Stuart Little ($133,000,000): I recognize that Stuart looks really great for 1999 CGI and that shooting in NYC is no cheap at all, but having such a large budget for a movie in which the biggest salary went to Geena Davis post-Cutthroat Island is quite baffling to me, specially if you think something like Babe (another movie with animatronics animals with CGI mouths) costed only $30,000,000 three years before.
- Adam Sandler comedies before his move to Netflix costed around $80,000,000, regardless of how cheap some of them looked... even some with actual production values like Click (Oscar nominated for makeup) and Little Nicki didn't seem to need THAT much money.
- Also on the same mindset, some of Michael Mann (Ali at $107,000,000 in 2001, The Insider at $68,000,000 in 1999) and David Fincher (The Girl with the Dragon Tattoo at *$90,000,000) might qualify, or even some weird outliers like *Cinderella Man ($85,000,000) or the plethora of 90s comedies with blockbuster budgets like the Williams/Crystal team-up Father's Day ($85,000,000), the romantic comedy shot like a Michael Bay movie Forces of Nature ($75,000,000) and The Haunting ($80,000,000).