Selling an effect should be the last thing on your mind... heck, it shouldn't even be IN your mind. Your main goal should be to create something that you will use for years to come. Before one can market an effect he/she must test it, test it, and test it over, and over, and over.
The effects that you see on Theory11 and other sites have been tested endlessly for months, and usually, years. You can't expect to create a best selling trick in 1 night.
If your main goal is to sell your effect, then you're doing something majorly wrong.
Mitchell