I don't think your numbers are accurate. I've know a couple of Hollywood writers. They tend to get a lot of money for a script. Most of their scripts get locked up in hold options, and never even get made. This is in the order of 100's of thousands of dollars, and it's all to them (minus the cut to their agent, manager, taxes, etc). The special effects, while in the millions, is a lot more money, is spread over a very large team, hardware investments etc.