There have been a few voices talking about adding ads to kbin. To those, I'd like to say they are probably not necessary. Mastodon is doing fine with donations (28k+/month and they do need more)

However, kbin has the advantage that it can add things like tips/badges or rewards, just like reddit. Gold stars, cake days, "highest contributor", "largest donor", "most active user", "most upvoted user", "guilded", "part of the donor club", participation trophies, and so on.

Instance owners could then connect a stripe account or some other donation service and allow people to credit an account in order to give away credits or tips or badges or something else.