I run an Aviation forum using Xenforo. It's been going for a long time (more than 14 years),mostly on SMF (free) but I finally got it converted to Xenforo in March last year.
I have always covered the costs of running the forum (virtual server, domains, DNS hosting, now Xenforo license as well) from occasionally asking for user donations. I'm a IT Engineer by trade, so managing the site and server (OS patching, backups etc) is easy to set up myself. As its a hobby, I don't need to make money out of the forum, and I don't want to limit access to the site.
I certainly could make money if I wanted to - one guy voluntarily sends me $160 US a year, he loves the site so much, and that's not the biggest donation I've had. It helps that the content is pretty unique. Its probably not easy to start a forum that is financially self-funding with lots of competitors already existing.
Xenforo is just better. My regular tasks are easier, site looks better, works better, configuration was easy, 99% of users love the change. The only downside to Xenforo is that third party addons can be expensive, and there are less free addons than in some other forums. Xenforo is a lot of code and functionality for the renewal fee. Some fairly minor addons can be a quarter or half the cost per year of the entire forum. So if cost is a problem for you, I'd make sure that the core stuff you need is delivered in the basic forum functionality.