I don't get it, is the value of hosting projects on your own servers worth the substantial leap in cost over GitHub.com?
Perhaps there are some companies for which Github Enterprise makes sense, but it seems like the number of potential matches for it being a really good fit is small. Most companies should just use Github.com or if they really need to keep the code out of "the cloud", just use plain old git with gitlab, gitorious or plain old ssh access control.
Stuff like that.