Stash is far, far cheaper than Github Enterprise, and Stash features have come a long way in the last 18 months.

* 250 user Stash license: $12000 first year, $6000 after [1]

* 250 user GH Enterprise license: $61750 per year [2]

If you need on premise git hosting, I'd look at Stash or Gitlab, long before I thought about looking at Github Enterprise!

[1] https://www.atlassian.com/licensing/stash#serverlicenses-1

[2] https://enterprise.github.com/features