We've used freelancers from both oDesk and eLance and have been disappointed with the results. Outsourcing content creation to those in other countries (with the possible exception of certain expats) may be inexpensive ($2-$5 for a 200-300 product description) but the results tend to be thin and with awkward syntax—obviously not written by someone with a native grasp of American or UK idiom.
On the other hand, those domestic writers—if they're any good—tend to want a minimum of $25 for a well-written and researched article or product description. There are also the considerations that 1) eLance and oDesk freelancers tend to charge by the hour or by the job, which can be problematical if you'd rather pay by the piece.
Here's how we handled the situation: We needed around 600 unique product descriptions for our Magento site. On my recommendation, we hired a very recent journalism school graduate at just over minimum wage (with a timely review) and provided enough research material to begin writing the things we needed. We taught this person the very basics of SEO (keyword placement, density, etc.) and—under close supervision—set the new hire to work. After roughly 2 weeks, the content was sufficient for posting after going through a thorough optimization process (employing whatever new Panda change MOZ.com had brought to our attention that week)
And after that review period, we gave our new employee a nice increase and we had an in-house content writer (Across all channels)—saving us a ton of money—who is learning SEO as an ongoing part of the education process.
