Relatively speaking, returning the materials to Earth is VERY easy. You need about 15,000 m/s of delta V to get from the Earth to the Moon. To deliver material from the moon to the Earth you not only need less Delta V for escape from the moon, but you can also aero-capture. This means you can get away with about 3000 m/s on the return trip. Probably less than a sub-orbital point to point hop on the Earth's surface.
However I imagine that returning the materials to the Earth would not be the initial goal. Probably they would be used for other Space related purposes. Fuel for Mars transfer, building Lunar bases and Colonies, etc...