with the new 3D style of flying, we can see plenty small planes fit with hi torque-speed servos. Those servos literally double the price of the plane.
I agree that on flight controls like the rudder there is a high force aplied during 3D figures, but I believe that in a lot of cases the servos are "oversized".

Modelers with low budget could be intersted in some reliable rules to select proper servos.....