Not OP but server costs are not that expensive in the grand scheme of things. A $5 DO droplet can easily sustain 500-1000 active users. If you were doing video

Not OP but server costs are not that expensive in the grand scheme of things. A $5 DO droplet can easily sustain 500-1000 active users. If you were doing video or audio streaming I could see concerns, but at the core of it all the server is doing is reading and writing strings and that's not a very intensive process. A $200/mo server could handle millions of daily visits, and you'd likely not grow further than that without running into the actual wall: labor. That's where things get dicey. You have to pay people, and ideally yourself, for the labor you invest into the project. As Tildes is a non profit it's already clear that the developer is building it out of love and not a desire to sustain his or her lifestyle. If the developer wanted a developer salary or enough income to hire another developer, though, I agree that donations wouldn't be adequate enough. That's when you turn to selling features (i.e. Reddit coins) or selling ads.