I agree, and think that this should be incorporated into the cost. Ie, a project twice as complex should be 5x the cost due to the additional management, comms

I agree, and think that this should be incorporated into the cost. Ie, a project twice as complex should be 5x the cost due to the additional management, comms overhead, permutations and potential risk. Said another way the curve is logarithmic and there's a theoretical upper bound on project complexity.