To some degree you will get what you pay for. There are also many who have no idea what the true value of a quality original artilce is. If you have an established site and can buy an article for $100, put it on your site and be listed within a short time in the top 10 for just one decent search term contained in that article, then you have made a killing. The true value of the article will be much higher than $100. If you have a new site and/or it sucks, it may not matter how good the article is, it may never rank. So there are many things to consider. Yes you can buy content for cheap, but for the most part it will not do you a tremendous amount of good. You can also buy expensive content that sucks, so you have to be careful.
I believe I know who gave you those prices Mark / Focal and if so, she has stopped writing. From what I have seen though, she was not bad at all. She was not charging enough.
It’s not a big secret that I write poker content, and I charge .20 a word. If I have to sell it for less, then it is more valuable to me to put it on my own sites. My proof of value is when something I have written for someone shows up in the top ten for a decent phrase. This happens often and these webmasters don’t mind paying because they have had the value proven to them. Many people won’t ever pay this type of money for an article, and that is fine, but until I run out of work, that or higher, will be the charge.