The goal with that is simply to make the edX self-supporting not to make a profit.
I see them creating two tracks based on the same open content: 1) a free not-for-credit track for informal continuing education and 2) a credit-based track with more stringent exit requirements (traditional final assessments and assignments).
For the latter, they will be able to charge quite a bit, if it's commensurate with a proper degree from an accredited institution.
The billion dollar question: how are they going to administer assessment for distance learners? The ability to securely and reliably administer tests by remote is the final piece of the puzzle to enable accreditable distance learning courses.
"Will there be an admissions process?
EdX will be available to anyone in the world with an Internet connection, and in general, there will not be an admissions process. For a modest fee — and as determined by the edX board, MIT and Harvard — credentials will be granted only to students who earn them by demonstrating mastery of the material of a subject."
Although your credentials won't say Harvard or MIT.