I know several people who are consuming mind boggling amounts like this. But I think at this point using the actual plant material is impractical as what they are doing is vaporizing extracted oil, aka "dabs".
I don't smoke anymore for practical reasons, but I have done one of these dabs in the past and it essentially incapacitated me to the point where I felt extremely uncomfortable and had to remain stationary for at least an hour unable to do anything at all.
My extreme THC consuming friends are doing something like 6-7 of these per evening and functioning fairly normally. This is what's mind boggling to me.