There was a thread awile ago similar, from that I got that the average consumption for MTL at 12mg was 5-6ml a day, for DTL at 3mg it was 20-30ml a day.
MTL less vapour, less liquid. DTL more vapour, more liquid. But the actual nicotine content amounted to about the same.
with DTL vapers using 4 times as much liquid than MTL vaper, and MTL vapers 4 times as much nicotine content per ml.