>you have to factor in the cost of installation, maintenance and update.

That number is about 10 minutes a month with a one-time setup of an afternoon, seriously. I've been running my own gitlab for about 2 years. Whenever my letsencrypt certicate warnings arrive, I go update them and then do a full update sweep on the OS.

I could also automate half of that by setting up automated OS updates, but the time spent administering the system is so low it hardly matters.