I'll add that sometimes the self-hosted version does something that the "official, paid"[1] version doesn't, or at the very least allows you to try to hack it together.

A problem with commercial offerings is that their idea of completed product is different than yours, and depending on the feature there's not enough $$$ incentive to pursue it. This is the major problem with Google, because search is such a ocean of income, that no other project will ever stand up to it.

[1] I say official because quite a few of self hosted versions are clones of some paid product.