I don't think he is just talking about the ground effect.

It takes more power to fly at 200 ft than at 50ft because of the change in air density. There is more air at ground level than high up. This means there is more air your helicopter can grab and push down. Also your engine is also getting less air and becoming richer. Gravity is decreasing. g=MG/r^2 ( I might be a little off since I haven't taken physics in 5 years).

The reason jets fly at 30-40k feet is because there is less air density which causes less drag on the airplane. The thrust from the turbines also decreases, but not as quickly as drag.