Space-based power

This question arose in connection with a recent post on the NextBigFuture blog which discussion thorium energy proposition advocated by Kirk Sorensen.

It seems that there's a lot of thorium on the moon, but beaming it back to Earth is a problem.

1. It costs a lot to install the equipment on the Moon.
2. The distance between the Earth and the Moon is such that losses will occur, so how much power actually arrives on Earth?
3. The value of power delivered at wholesale prices is only about 40 bucks per megawatt hour.  It isn't all that much economic value, which is what you would want in order to finance an expensive project on the Moon.

Those are the problems that I can think of, perhaps that is only scratching the surface.

No, what we want to do is to replace costly stuff with less costly stuff.  This gives us an advantage that we wouldn't have otherwise.  How to do that on the Moon?

Since there is so much thorium on the Moon, and it could produce quite a bit of energy, how can we use this energy?  Especially since getting it all the way back to the ground would entail losses and wouldn't be any cheaper, and probably be more expensive than what is already available.  Here's is a proposition: beam the energy to a spacecraft which uses it for propulsion.  Why would this be an advantage?

1. Beamed power means that you don't have to carry propellant.  It reduces mass penalties.  The cost per pound to get stuff into orbit is still pretty high.
2. It would facilitate the use of electric propulsion devices, such as VASIMR, which use only small amounts of propellant, further decreasing the mass penalty, thus saving even more money.
3. The cost of the lunar produced energy has to be less than what it costs to beam energy from the ground.  Even if lunar produced energy is more expensive than ground based energy, it must be cheaper to get it where you need it, since there is no atmosphere on the Moon.  This cuts losses, thus saving money. 

Therefore, you can mine thorium on the Moon in order to produce energy that can be beamed to spacecraft traveling to and from the Earth.  This will reduce the costs of traveling between the Earth and Moon and help facilitate commerce between a lunar colony and the Earth.