Why are visual effects so expensive?
I'll tell you why.
Time.
Time cost money.
My time isn't a democracy. I control it. I get to decide who gets my attention. Hollywood wants our attention. They have had it for a very long time. It's where all the stories are.
Concept artists get to think up and visualize worlds that you have never seen. Pre-vis artists add motion and depth. 3d artists take 2d and give it sides. Texture artists make it dirty and real. Compositors take all the images and make them one. Coordinators watch over the artists. The IT folks keeps all of this running. Vfx producers provide foundation. Last but not least the visual effects supervisor. They keep all of us honest. They make sure our work is good. They are looking in the corners when your looking in the middle. They live in A and B.
That's a lot of people's time. Yeah, visual effects cost money.