If you wanted to self host Lemmy is very lightweight. The general consensus is you could get a cheap virtual host for $5-10/mo
That would cover yourself and a few friends. Now, if Lemmy were to really get popular your database would grow in size so youay have to get more storage later but it’s overall very inexpensive to do it yourself.
That said, major instances like Lemmy.world could charge their users $1-2/mo and probably be fine (this is napkin math). Long story short nothing is free, even if it’s relatively inexpensive. We need to create a community that is willing to pitch in a few cents for freedom. I don’t think that’s too much to ask, otherwise the ad model comes into play and the place goes to shit.