For my money site, myself. I do have a writer, and I get a few articles from her once in a while. She's the only person I trust with content for my money site. $1.80/100 words, she's a GREAT writer. But generally speaking, I write the articles myself. I outsource just about all of my SEO and linkbuilding, so I don't really need to write articles for web 2.0s; that's taken care of.
It really depends how much you're willing to spend.
Some get bored writing, but I actually get bumped. And I space it out so I don't get bored quick. Instead of doing 20 articles in a single day, I do one article a day for each of my sites. Plus, the way I look at it, each of these articles will eventually bring me long tail traffic, which equals money. So well worth it in my opinion.