I've made about $3k a month in semi-passive income from my codecanyon portfolio in 2013. I call it semi-passive income because I have to spend some time on support each day, but it usually doesn't take more than 30 minutes.
I sell on codecanyon as well though only make around $300 a month right now. I have almost the same number of items as you do yet can't seem to get the visibility. Do you have any tips you can share?
Also, completely agree about the semi-passive! Lots of questions to deal with daily.
In my experience quality sells. Quality code. Quality feature set. And most importantly, quality design. I think a lot of items on codecanyon neglect the design aspect and therefore don't sell as much as they could.
Also, I've been somewhat lucky in that almost all of my items have been featured. This probably has something to due with how much time I spend on design - at least 40% of my total development time is design. Feel free to email me with a link to your portfolio if you want some specific pointers...
I build things that scratch a personal itch. If there's a product that I need and I can't find a suitable existing product, I build it and sell it, because I assume other people also have that need. That's how Duet was born - I wanted a self hosted project management app that was functional and beautiful. I couldn't find one, so I built it myself...
EDIT: My portfolio http://codecanyon.net/user/23andwalnut/portfolio