The notion here in Japan is with our manga culture and massive art schools, the idea of "anyone can draw...only few can create" is rigidly intact.
Let's start this step by step... So a certain anime is based on an original story (manga). To simplify things, I'll use "Inuyasha" as an example. The anime "Inuyasha" is based on the Ms. Takahashi Rumiko's manga of the same title. It is her creation, as she thought up of the story of Kagome and Inuyasha, the whole atmosphere of the Inuyasha world, etc. Instantaneous as with her previous works, "Inuyasha" became one of the hottest mangas on Weekly Shonen Sunday, where the manga is serialized. Informations regarding manga artist income can be found here: http://forums.animesuki.com/showpost...07&postcount=4
After several successful releases of manga tankoubons, Sunrise decided "Inuyasha" was a good opportunity to capitalize upon into animated form. Officials at Sunrise will go over to Shogakukan (publisher of Weekly Shonen Sunday) and negotiate. As with other collaborations, profit margins and royalties are split between the anime company, the publishing company, and the manga artist.
Why doesn't money go to key animators? Because they just draw from a set of instructional guidelines. Key animators were not the one who thought up of the idea. In a sense, they are just as same as corporate warriors - instead of sitting in front of a computer with an Excel spreadsheet, key animators sit in front of a computer and draw with a tablet pad. The idea is rather not much different from any other industry. Think of it this way - who usually gets the money when a person invents something and a company mass produces it? It's not the guys who actually make the stuff at the plant - it's the inventor and the company that chose to invest in that invention. The guys at the plant get paid a fixed salary no matter what they make - the key animators get paid a fixed (a horridly low) salary no matter what they draw.