BUT again: more RPM, more energy. So, if you could get the RPM's down, couldn't you put the consumption, down, too?
A good way to think about where the energy in a car goes is to break it down in to three catagories:
1) Engine losses (i.e., how much of the energy that goes into the engine/motor doesn't come back out as mechanical energy).
2) Aerodynamic drag. This depends on the speed and the shape of the car (and how dense the air is), but not the engine/motor.
3) Overhead. This accounts for stuff like the lighting, HVAC, turning the flywheel in an ICE, the radio, etc. It doesn't depend on speed.
ICE cars have pretty high overhead, so as they speed up they become more efficient for a while, because they're amortizing the overhead over more miles. Electric cars, on the other hand, have very low overhead (unless you're running the HVAC, especially the heat), so as you speed up they don't get much more efficient.
Losses to aerodynamic drag per unit distance go up with the square of speed. Because of that, as you get moving they grow really quickly and start to dominate everything else. In an ICE car, this effect is competing with the increased efficiency of amortizing the overhead, so you're going faster before you hit the tipping point. In an electric, there's much less overhead so the peak of the efficiency curve is much slower.
There is some additional engine loss at very high RPMs for electric motors, but it's not that huge. Changing the gearing would help that, but since it's a tiny component of the overall energy budget, it won't help much. You'd do better to spend your money trying to reduce the coefficient of drag, say by lobbying to make it legal to replace the side mirrors with cameras, or adding fairings to the wheels.
To be clear here, the discussion above might make it sound like it's better to have high overhead because it makes it more efficient to go faster. It's not. What's going on is that the electrics have to work with a much lower overall energy budget. A gallon of gasoline has well over 30 kWh of energy, so a full battery pack in the Roadster has only 1.5-ish gallons of gas worth of energy. Because the electric powertrain is so much more efficient, this is results in decent range even with pretty low overall energy.