I'm not saying its a blessing, but it's a fact.
You say bigger turbos and power need more fuel and will be more thirsty, and all I'm saying is the lower half of the fuel map is quite the opposite it will probably have less fuel in it. So if you drive in these areas if the fuel map you won't use more fuel at all!
Stage 1 is great if your not after much power. If sticking to a T3 I would always advise 803 greens where possible as they suit the T3 perfectly and it can be allowed to work a little without the issue of going lean which all stage 1 cars will have because the Injectors are too small and the boost will have to tail off at high rpm to keep a stable safe afr
If you cruise a stage 1 car at lambda 1 and then swap injectors and do the same with a T3 803 setup the fuel consumption would be identical as the engine will need the same fuel quantity to run lambda 1. Only becomes heavier on fuel if driven harder.
More power doesn't always mean worse economy. I just depends how you use the car.