In my line of work, 50,000 words is the easy part. Getting it down to the 5,000 or 10,000 words that are important, and having those be well-written, is the hard part. In fact, that is what I am working on right now....cutting a bunch of text on Antarctic glaciation back by about 50%. This is extra difficult because I keep figuring stuff out and having to read papers as I am writing.
Chris