As mentioned, some writers haven't even been working here an entire year as of yet. Mayb itz bcuz of they'er "spelink nat rekwired" writing abilities?!! Or they only started here recently. Who knows ?!!
However, you'll find a large pay difference between many writers here. Part time and full time writers alone can send the numbers all over creation.
Your original question / Limitation "here in oDesk" is how you increase it. Get past that when you can. If you were only looking for writing work on odesk, you were already defeating your own purpose by not checking out as much as possible.
In my case, I have only been working on odesk part time as a writer. The rest of my work as a programmer, PC repair technician, and others shows up at random right at my door. And then I have my work as a gamer which also includes writing jobs. I'm not exactly rich in all this but I don't miss out on my 3 meals a day, bills paid, or my fun just the same!!
I'm gonna have to add Farmer to the list one of these days!! With any luck, it'll be soon because that's a really big farm I'm currently putting together!!
Back in the old days (around 2011 to 2013), given the cost of living in the State of Florida USA, a writer could easily make a living working full-time via oDesk.
Note: Though not a writer these days, that's how I started on oDesk (writing Web content and writing for purposes of Web presence marketing, SEO, SMM, etc. -- blogging, guest blogging, technical reviews and whitepapers, corporate level press releases, etc.; no "creative" writing to speak of).
Before going freelance, I always thought of "writers" as those associated with fields of work like journalists, editors, etc., with various types of media firms. The world of "freelance" has given the word "writer" a much broader meaning.