You're very welcome to switch to GitLab.com, we are free forever https://about.gitlab.com/gitlab-com/#why-gitlab-com-will-be-... and it can import directly from GitHub.
However for a bigger enterprise they require more functionality here is a comparison of the differences between the Community and Enterprise Editions.
https://about.gitlab.com/features/#compare
Several pricing options for EE but essentially the base cost is $39 /year per user.