If people have to pay you'd have much less bad content to begin with - only the very dedicated trolls would actually put real money on the line to get their shit posted.

The problem is that we are both approaching this as a problem that needs to be solved, while in reality it only needs to appear like one.

Social media companies make their revenue out of "engagement", and posts breaking the rules often generate the most of it, so properly moderating them would actually hurt their bottom line by more than just the cost of said moderation.

These companies are incentivized to leave as much "bad" content up as they can (as it generates engagement) while making it look like they are taking action as to not risk bad PR or legal consequences. Same goes for deterring or punishing offenders - long-term bans are trivial to implement and would significantly deter breaking the rules, but would also decrease "engagement".