Everyone has their price. You just have to find the point where an addition person on that flight would voluntarily get up.

Put it this way, how much did the incident with Dr. Dao cost? Actual costs to him and bad publicity causing people to not book with United. Yes, it is hindsight at that point, but a track record built up for future events.

What would it have taken? A few more hundred dollars? A couple of thousand more dollars? Certainly they would have reached a price for one passenger at less than say a free pass for a lifetime. (I am being silly, intentionally.)