Not usually - if they brag about it they are usually told to shut up and go use the remaining three weeks for revision.
Besides if they finished 50,000 words in a week flat they have a lot of time on their hands meaning they never leave their laptop and they are up the entire week. When I tried it in 2008, I would write 800-1,000 words at a time then sit back and stare at it and try to sum everything up to that point in my head then decide where the story should go from there until I got to the next point at which I had writer's block. If you want to get uber serious - you must read hardcore novels of various genres, carry a notepad and pen with you and jot down sayings and ideas from everyday life, and you dedicate yourself to a daily word push and you willingly submit your works to the forum for proof-reading, editing, revision, and suggestions from other forum members and expect to get flamed at least once a week. Some actually force themselves into 'self-bannination' so they have no other choice but to sit and write. It's not uncommon for these folks to spend 18 hours a day sitting and writing, especially if it's their main source of income. I would have loved to have become a professional writer but it's very very hard to make a full-time living at it. Many members also have their own blogs which they may or may not receive money from. Many use WordPress instead of Blogger, as WordPress is seen as more professional.
Sometimes I wonder if I could ever become the next J.K. Rowling - single mother wrote her stories down on napkins and what not while raising two kids.She had her novel turned down repeatedly until one publisher decided to take the risk and bam! Now look at her - she is not going to hurt for money at all for the rest of her life.