The movie's origins are somewhat arbitrary. Lucas screens all the footage in a private theater and said "this looks nice on the big screen, everyone should see it this way." So they initially took a multi-episode storyline and strung the episodes together. But as the project went along they expanded sections and added scenes to make it cohere a little better as a "feature film." Seeing as each episode has a pricetag of a million dollars or so, this thing probably costs less than ten million. There are at least forty or fifty million dollars worth of kids and fanboys out there, so from Warner brothers' point-of-view that means "cha-ching!"