Have you ever thought to yourself, "Film and photofinishing is expensive! I wonder why?" I'll tell you! In story format!
Today somebody brought in some film to be developed. He said is was a old, so I figured it'd be like most old undeveloped film. The prints would be a little red, maybe purple.
You know that brownish color negatives are? Usually if they are left to sit before being developed, they go greenish. These ones did not. They were purple. Not the dark purple of C41 black and white. Light purple, almost lavendar.
Yeah, I was shocked too. However, I'm a lab tech, this is our kind of fun. We get to try and figure out why this happened and how to fix it! What happened I know, it was old - it might also have been exposed to x-rays, heat, extreme cold, or water! I fed it into the machine. As I the prints were green. "Why Green?" you ask? That's the way negatives work! I'll show you:
Red<->Cyan
Green<->Magenta
Blue<->Yellow
So you can see, red becomes cyan on negative, green becomes magenta, and blue becomes yellow. So a negative with a strong magenta tone will be a print with a strong green tone. This was more lavendar, so it had some yellow in it as well.
This is what the first print looked like:

Greeny-yellowy. I thought to myself, "maybe it was supposed to be black and white... it's just colored for some reason."
So I made it black and white:

The prints still looked a little iffy, the colors were off. Even the black and white still seems a bit wrong.
So I did the thing they pay me money for. I tried to correct the colors. I pulled out lots of yellow, cyan, and magenta. After removing five levels of cyan and magenta, and 12 levels of yellow I got this:

Still yellowy, but I couldn't remove any more, the program was at it's limit XD. I darkened it up a little bit, but not too much. His arm is a bit washed out, but anymore and I lose the face. It's a complicated thing trying to fix film.
"So that's why photofinishing is expensive! They have to try and make it look good!" You're thinking. We'll you're wrong!
Film is mostly silver. Silver is expensive. Therefore film is expensive. Photofinishing is expensive by relation.
=D