My intuition is that this will be a terrible idea, 100% the "Road to Abilen" can happen. 0% signal because everybody is playing "safe" being politically correct. At least that is my prediction for the time being. I usually find your odeas really good but not this time

I'dont offer any proof, just my intuition. I think a variation of what you propose is chargeing per-interacion like stacker news does but giving the relays room for exploring different prices and models. Some can be extremely expensive to post in, probably fostering long and dense content and other may be cheap and offer some spam prevention since you need to pay for posting, boosting, etc...