If anyone doubts this, just take a look at what Khan Academy currently offers for a fresh perspective. Make an account and click around (https://www.khanacademy.org/signup); it should be easy to see that a ton of effort went into making this and, as far as I can tell, they run purely on donations. I wouldn't be surprised if the current cost of operating Khanmigo is just being passed along by Khan Academy at no markup, or even a slight loss.