Tiffany and Wendy have provided excellent answers. I hope this doesn't derail the topic.
I only work fixed-price for writing gigs, despite the fact that half of them are hourly. If I'm interested in the work (because the work is interesting, not because of the pay rate), I'll propose what I think the work is worth to the client at the quality I can deliver. For example, one client paid me $150 each for 10K word stories. I wanted the practice, they rarely took more than an afternoon to write, so I accepted.
I turn down well-paying easy work for which I'm qualified, such as blogging on medical topics. I'm unlikely to learn anything with the job, and I already get into too many p*****g contests on a forum where everyone feels qualified to diagnose mental disorders in seconds.
When I'm hired to write a professional business paper (never on UW), pricing per word is just plain wrong. Executives want short, powerful and clear documents. I'll often write 3K words, perhaps eleven pages, then spend a week cutting it down to three pages.
I've stopped ghostwriting for the most part. A UK client (another board), whose own atrocious writing was in British English, asked for a romance set in Britain. I wrote it, made sure to use idiomatic British English, including separate dialects for two main characters from separate classes and professions, and every detail was thoroughly researched. She wasn't happy. "I didn't expect it to be in British English."
