StackOverflow for Teams seems like a really hard sell too. $5-10/user/mo is pretty steep, especially for a service that needs a significant-size userbase to "work".
Just seen it adopted in a F50. It's not particularly difficult to sell in my opinion. The product is pretty good too.
We use StackOverflow for Teams with a small team (<15 developers) and it’s been great. While I’m sure our revenue alone won’t make it profitable, I think it’s a product that can work with teams of all sizes. Don’t knock it till you’ve tried it.