I work in an org with 8ish FTEs, a handful of student workers, and like 200 volunteers. Almost every service wants $5 or more per user per month, that's $1,140 per month per service. We selfhost open source solutions for everything we can and sometimes have to write something in-house to meet our needs.

That sounds an awful lot like, to you, that is the "very big financial cost difference" I mentioned.