Of course no reasonable person is saying that you have to compare against the worst thing, that's stupid- I was simply stating that I've seen things that have easily quantifiable returns.
I'm comparing it against the 'nothing' that I would otherwise have.
If you're comparing something then that's yours to compare, and this is a tool for doing that.
if you're not running github or gitlab, what are you running?
Maybe SVN+jira? or gogs? or gitea? what about teamcity?
I'm not going to break down the cost savings and expenses of each of those, I'm just saying we're all already using services that have saved us many hours a week compared to those services not existing in any form.
Its up to you to debate the 'many forms' a service takes, and remember that server hosting and human time is not free, so something self-hosted that requires some hours of time to maintain needs to be cost controlled for.