I object MITx as being called MOOC.
It is not . It is the first top school to offer online . Therefore they attract millions globally.

MIT is a top school, therefore it attracts millions, already they have 100,000,000 captive customers around the world due to Opencourseware project started in 2001.
Therefore cost per student is nill, I believe less than $ 1 per person .
If MITx charges only $ 10 for exams they will make billions $ . It is good. Therefore project is sustainable .
Plus they provide certificate which is better than a credit. We, employers, value a certificate from MITx very very highly.

So sure it attracts millions and billions .
Stanford, Yale , Princeton on the line .
MIT has a wonderful long term strategy regarding online. They will provide degrees as well when the right time comes .