I think you have framed the problem incorrectly. If you are given the option to either make your course paid or fee you include people who are motivated for different reasons. If you wanted to create a free class, would the fact of having an option to create a paid course motivate you any less? I think that codecademy should create a structure similar to Apple's ibooks platform where you have the option to create paid content if you so wish.

Codecademy is smart - they realize that collecting use/accomplishment data on high-quality lessons carries much more upside than trying to sell the content created on their platform.

How is this smart?

Either you get money directly, or your left trying to monetize -accomplishment- data? Are we expecting the ad-market targeting newbie programmers to explode or something?