I don't like writing content. I'm slow, get bored quickly, have constant writers block and simply would rather do other things... any other thing.
Getting decent content isn't cheap, but since I'm so unproductive when I try to write, I find that it is generally better for me to purchase content.
The quality and quantity of the content I purchase depends on how it will be used. In my money site, I will pay more for longer, high quality articles. For backlinking, the further from my money site the link is, the lower the quality of the content.