After 10 years, I'm finally realizing that I have a comfort zone when it comes to word counts. At least when it comes to magazine articles. I'd much rather write 1200-1500 words than anything much longer or shorter.
When an editor wants me to write front-of-the-book type stuff-- 400 to 800 words or so-- I cringe a little. I know it's going to be just about as much work as the longer stuff, for less pay. I'm still going to have to do interviews, I'm still going to transcribe them, I'm still going to write the same meat of the article... and then I'm going to struggle like crazy to trim it down to what almost always seems like too small a space for the topic.
Worse, though, is that there seem to be many editors who cannot grasp that 400 words is not enough to pack in everything they ask for in their brief. "Please write the entire history of the the automotive industry, and a sidebar about bicycles" is just not do-able.
So then I do the mental equivalent of stuffing 2 weeks' worth of clothing into a small suitcase, sitting on it and jumping on it and breaking into a sweat trying to get the darn thing zippered. Then I get the editors' follow-up questions: "This is interesting, but you haven't mentioned why tires are round, or the name of Henry Ford's great-grandson, or why puffy dice became a rear-view-mirror fad." And I have to reopen the darn suitcase and figure out how I'm supposed to stick MORE stuff in it without making the toothpaste explode.
By the end, I'm just closing it up with duct tape and a staple gun. The resulting word count is almost always longer than it was supposed to be, because there's just no way to do it otherwise. But I still get paid for the original assigned count, unless I manage to negotiate otherwise during the request for revisions. (If the editor is asking for something outside the scope of the original assignment, I can try negotiating for more money at this point. Otherwise, I'm pretty much out of luck.)
One of my fantasies involves my asking an editor what word count she wants, and having her reply, "Oh, you choose. I trust you. Heck, we'll just wait until your article arrives and format the rest of the issue around it."
That comes right after the "we'll-pay-you-$5-a-word" fantasy.