NWSRG,
I think that you are getting confused with the use of one position, this doesn’t mean that the aircraft is using the same amount of power each time, as
tired explained
at take off, the T/Ls are placed either in TOGA if you're doing a max power T/O, or in Flex/Max Continuous detent if you're doing a Flex power T/O. When the levers are in either of these detents the FADEC will give you the max power available for that selection (It depends on the ambient conditions).
This is pretty similar to Boeing aircraft in that the amount of thrust required is calculated for every takeoff based on the weight/runway length/temperature/altitude/thrust rating. The difference is that on Boeings the power levers are set to a variable position by the crew or A/T, on an Airbus the crew just set the power levers into a detent.
They are completely different philosophies of doing the same thing, you will find people who love or loathe both methods.
Mutt.