You're right makeloot.
however if a writer who knows nothing to begin with, about "acid diet" for example, start to write on this topic for more then 10 articles, he will quite understand the topic, enough to create quite decent articles.
I trained a friend of mine to write and I gave him 'diabetes' topic, and in just few days, he can write an 'almost perfect' article about diabetes. He started with zero knowledge about diabetes and almost no writing skill. He didn't know what the heck is adsense...
When I say 'almost perfect' I mean, it's just an article for us, common IMers who will use it on a common blog monetized with adsense-cpa-affiliate.... or to submit the article on ezines, so no need to hire a professional diabetes expert.
So yes, it comes down to what do you want it for, what is your purpose. No need to pay $15/article if you only use it for ezine. You can get a quite decent multi nested spun article with that rate
But yes, I'm talking as a common "blogger", I don't run an authority site.
Anyway, I just found another 'good' writer at $3/500 words rate. Ordered 5 articles on a really uncommon topic (a product I don't even know it exist, lol), and pushed him to finish it under 3 hours (it's a test anyway), and he made it. his work is quite good for that rate, he knows about basic seo-ed article, keyword density..., and the article flows smoothly. Enough for my MNB *micro niche blog*