Cosmetics.
Let’s offer paid cosmetics for users of your instance. Animated or custom banners, posts, new themes, etc.
It’s a model that works really well for Discord and League of Legends. Instances offering to sell aesthetic luxury to their user base could work for Mastodon too.
It’s non-invasive, it’s optional, it’s a great addition for some people, and it allows to raise funds to keep the hosted instances up and running.
Do you think it’s viable?
I see monetizing as something different from covering cost.
I agree that costs need to be covered somehow, but monetization is about making MORE money than is actually needed to run the platform and that is definitely the Achilles heel of existing social media that doesn’t need to be carried over to Mastodon.