A realistic Huey UH1-H (source DCS flight manual, so if not totally accurate, it is pretty close) has an internal fuel tank of 770 liters, and it's calculated fuel consumption rate is 318 liters/hour. That means flight time of around 2 h 30 minutes, so 10 min flight should have used about 6 % of fuel.

And the ground vehicles. When driving around I've noticed a difference in fuel consumption whether driver uses full throttle or not (with keyboard controls the difference with just W-key and shift+W -key). It's like the difference between a Sunday drive to the store and driving in a race and results in a drastic difference in fuel consumption. The same really should be true when driving on level ground vs. going uphill.

I do agree that the fuel consumption rates are off (the biggest oddity I can remember at the moment relates to the BTR when it's in the water), but a little more detailed study of the issue is probably needed.