I think the problem on the relay side is that at a point it will become more expensive to scale. Currently you can run relays on a relatively cheap VPS but eventually you are likely to need clustered backend databases, multiple front end servers and load balancers to handle load. One time payments for relays won’t be sustainable so they will need to move to subscription models. The same scaling issues for image hosting.
I have a thought that for content creators and relays the solution might be content creator specific relays which charge a small fee per event written. A split of the fee goes to the relay operator and a split goes to the creator. That way it supports both without requiring additional zaps on top.