Not actually true. You're correct that it is cheaper to get from earth to low earth orbit (LEO) than to the moon. However it is cheaper to get to LEO from the moon than from earth. This has nothing to do with altitude; it's a function of the delta-v budget -- or the amount of momentum change that is required to get from one place to another:

http://upload.wikimedia.org/wikipedia/commons/c/c9/Deltavs.s...

As you can see, getting from earth to LEO requires 9.3-10 km/s of dv, depending on the type of rocket you are using. All of this must be high-thrust propulsion, otherwise you'll immediately fall back to earth. 9.3-10 km/s of high-thrust propulsion is indeed quite costly to implement.

On the other hand, to go from the lunar surface to LEO is only 5.5 km/s of dv -- and only 1.6 km/s of this (the trip from the lunar surface to lunar orbit) needs to be under high thrust. The rest of the dv can be done with relatively inexpensive low-thrust techniques which require little or even no propellants -- such as ion propulsion, solar sails, and aerocapture.

So to a rough order of magnitude, it's 2-6 times cheaper to get to LEO from the moon than from the earth.

Edit: miscalculated the lunar surface->LEO dv requirement.

I know nothing, but I would think gravity smelting and related operations would be much more technically difficult and risky than gravity based operations on the moon.