gosh,maybe its the beer but I am having trouble understanding your post. Nothing against you, sometimes I cant decode what I read.....let me try to answer best I can.
I assume you are asking what are optimum altitudes to fly at and how much extra is burned if we are not at them.
I will keep this as simple as possible as what I will say applies to all aircraft piston/turbine, flying transonic-subsonic.
To operate an aircraft efficiently, all aircraft need to achieve various forms of optimums,some of these are:
1.Optimum Angle of attack
2.Optimum engine speed (optimum RPM/optimum N2)
A.If flying below optimum altitudes. The Angle of attack of the aircraft will be lower than optimum because the air is denser.
The lower angle of attack means that drag is higher than if the AOA was higher. The solution, Slow down. But if you do that,your flight time goes up and so does your fuel consumption.
If flying above optimum altitude. The angle of attack will be higher than optimum and again, drag will be higher. The solution is to speed up but then fuel burn will increase above optimum as well.
(Low AOA drag is caused by parasite drag while high AOA drag is caused by induced drag)
B. Optimum turbine speeds for jets are the low to mid 90's
If flying below optimum altitude, say FL250 on a generic jet you may only need 83-88% N1. Your turbine speed/ground speed will be low but your fuel burn will be relativly high.
If you are flying above optimum, your turbines will be straining more than necessary for thrust and therefore need more fuel
Think of it like you are driving your car. Less than 55mph(optimum)
you are going slower than optimum but not really getting much out of your gas mileage. If you go above 55mph your fuel flow will increase out of proportion with speed.
Did I confuse anyone? Im confused!
If you want to know more about this fascinating topic try and pick up 'Handling the big jets' NOT 'Flying the big jets'