Moon Express plans to create a robotic lunar hydroxyl mining machine. It will fill a small fuel tank then it will launch into lunar orbit.
A second lunar robot lander will use the lunar orbit fuel to lower the cost.
Then there will two robotic lunar lander-miners
This will continue to four then eight lunar landers and a large lunar orbit fuel depot.
Then when the setup is large enough a lunar fuel depot will be towed to low earth orbit where it will be a low earth or other earth orbit fuel depot where it can sold to other companies and missions.
The cost of space exploration would then approach the cost of launching to earth orbit.
SOURCES- Arxiv, moon express