^ Just look at The Host, Shin Godzilla, or Cloverfield. Sure, a few of those are foreign films and as such have had limited play that can't necessarily be called mainstream, nevertheless I've seen them go over like gangbusters with audiences besides your average monster or kaiju fan. By Hollywood standards they were cheap as hell. All it takes is smart filmmaking, and a slick, engaging film can be made for far less money. In other words, concentrate on what you know you can pull off and do it well.
Just imagine how much less Godzilla: King of the Monsters would cost if they eliminated half the cast, subtracted, say, Rodan (even though he's my favorite monster in the movie, he's the least necessary for the plot), and just concentrated on making the human element very engaging, maybe by having Millie Bobby Brown as the audience identification character and having her have actual relationships with the people in the terrorist organization, who are actually characterized an interesting instead of faceless goons? If you make the humans interesting you could have shaved off 10 minutes of monsters and no one would miss it.
Let's take my example of making a Keanu Reeves action movie with Godzilla. John Wick 2 still has the most impressive an incredible action of the series, and that movie cost about 50 million. Now imagine you had an additional fifty million for 20-30 minutes worth of monster footage.
Shazam cost $100 million. That's half as much as the big superhero movies these days. People liked the story, so they didn't care it was less expensive. Warner Brothers even had the confidence to keep the big special effects sequences from the second half of the movie out of the advertising so as they'd be a big surprise!