As the memory fades away, Charlie Stross wrote about the difficulties in going back to the moon:
Not only does the cost of putting a payload into orbit increase with the cube of the payload weight — this rule holds true in the opposite direction, too. Stick a LEM on the moon and bring the contents back? Easy. Increase the mass that the LEM brings back? Very expensive — the price goes up as the sixth power of the weight you’re returning from the lunar surface (because you have to loft the heavier LEM into Earth orbit to begin with).