[El Gato]

The superconductor causes the gravity to stop

No it doesn't. Rather the magnetic force opposes or counteracts the gravity force. The gravity is still there. This is no more magical than the fact that you don't slide to the center of the earth every time you try to stand up. The mechanical forces in your legs oppose the gravity forces, just as does the magnitic force in that superconducting "levitation" demonstration.

[Frank_Discussion]

Half answer there, El Gato.

1. When room temperature super-C materials come of age, then energy input will drop to nothing.

2. Current materials require active refrigeration, so there is power used to keep everything cold, at least. And the more common SC requires some sort of current run through it. That said, the latter "current" material can be formed into electrical windings that will hold an initial amount of energy that you pump into them, until you decide to bleed some off. For what we're talking about, you'd charge up the system to get a self-contained electromagnet. As long as you keep it cold and don't remove any stored energy, it's on-line. (I've worked with this technology, in the mid to late 1980's there was some research in using it as a storage system for electrical transmission.)

You're absolutely right - no magic here! It's just not common knowledge.