Why do people assume creative jobs are easy?

Jobs like fashion, music producer, artist, designer etc.... People don't realize how much work, time and thinking goes into our work. I designed a 29 page medical brochure for a client. This project took 7+ hours to make. Took a lot of creativity and time to get this done within the timeline he wanted it. I am charging him $200, which is a pretty cheap for a brochure design. However he wants $200 for two 29 page brochures and a smaller brochure. That is not going to happen. I've been screwed over so many times in the past doing freelance work that i refuse to budge for this one.