Very true, there always being a cost somewhere is a general rule for all services in general. Its the reality of computer infrastructure that theres gotta be a computer/server somewhere eating bandwidth and energy, and someone with enough time + technical knowledge to maintain them. Those cost need to be offset either through donation or profit, or the service provider just has to eat the expenses and pay out of pocket. ‘no cost actually’ is in reference to the end users directly paying for something with direct money or collected private info sold to ad companies. In many public hosting instances for open source services most active users don’t pay or donate at all and get to use the service without their info being sold. In these cases the expense is split between a few donations from better off charitable users and the rest is out of pocket from the sysadmin who most likely has a real job that pays well enough they can eat the hosting fees and not worry about it.