Actually I would say the same amount of work was done. Work done is basically force times distance. If the car is raised to the same height, the same work is done. In the second instance, it is just done less efficiently so more energy is used but the gain in potential energy is the same.
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Yes, the same amount of work is done in raising the car, but only if you ignore the work done that
doesn't contribute to raising the car.
In the real world, a (petrol) car raising itself through (say) 1,000ft wastes about 80% of the energy used because it also converts chemical energy to heat energy. If only about 20% of the chemical energy is actually converted into gravitational potential energy, then only about 20% of the work done by the car results in the increased potential energy, since energy used is equivalent to work done.
A car's energy efficiency is considerably lower at 70mph than at 50mph. Therefore, the higher speed results in relatively more energy being wasted in the form of heat. In our experiment, more energy will be required to achieve the same gain in height, which in turn means more work is done by the car than when it was travelling at the lower speed.
Since the human body is also a machine that converts chemical energy into other forms, returning to the OP (on this particular subject) will show that the treadmill had it right all along...
And another thing that I sometimes think about... 
I've noticed as I walk along country lanes (and I used to notice it when I cycled along them) is that beetles tend to cross the road at a perpendicular angle to the edge of the road. In other words, they take the shortest line to the other side.
Now, for a beetle, a road would be roughly the equivalent of what a human would experience as a two-mile expanse viewed from a hands and knees position. Also, a beetle's eyesight isn't that good. So how does the beetle know the direction that results in the shortest crossing?
My theory (and the only one I can come up with) is as follows: Some kind of local natural selection is occurring - and beetles can navigate, perhaps by using the Earth's magnetic field. Since the shortest route is the safest, beetles that do not cross in a perpendicular direction are more likely to get squashed, while those that do tend to survive and reproduce. And that accounts for my observations, which go back many years!
