The moon is much further away. Just a hair shy of 385000km, versus a peak of about 450km for the planned LEO stations.
Distance within a gravity well is a major issue; the moon is still inside Earth's gravity well, roughly 0.0027 meters per second per second...
This means having to hit a velocity high enough to not stop until gravity of the moon captures it. That means more fuel per unit payload. That means bigger launchers and/or more launches.
The ISS - an LEO Station.
The ISS was assembled from over three dozen missions's efforts; over 2 dozen carried significant superstructure units. It can house at best a dozen people. It's not self sufficient. It is one of the most expensive habitation units ever built by mankind, and per capita, probably the single most expensive.
Oh, and it's about 450 tons. ①
So what portion of LEO mass can we expect for Delivery to the moon?
About 1/10th. Here's the math...
Let's look at the Saturn V. It was capable of delivering 118 tons to LEO, but only 47 tons to translunar orbit insertion (and the payload has to stop itself at the moon, at that).② The Apollo-Saturn missions were essentially 6 stages. The S-1C first stage, the S-II second stage, the S-IVB third stage, the Service Module as 4th stage, and the Lunar module is two (descent and ascent). Each of which is a rocket. Without the SM, figure the SIVB would launch even less to the moon. The actual payload to the moon was the command module and the lunar module; the service module is actually essential rocketry as well as essential support for the CM.
So... let's assume 7500kg the CM mass is the 4th stage to the moon, and calculate the mass to the moon of useful lunar payload.
LM Mass: 14,696 kg
SM Mass: 24,523 kg
CM Mass: 5,806 kg
Remove: -7500 kg (Fuel, engines on SM, estimate)
Total: 37525 kg to lunar orbit.
The Descent stage is about 10,500 kg ⑥, of that roughly 14,700 LM, or about 71% descent stage. So, using the same ratio upon that 37525... we get about 10700kg to surface... from a Saturn V. About 1/10 the payload to the moon as to LEO
The best current heavy lift launchers only get 23 tons to LEO; the Falcon Heavy is supposed to get 53 tons to leo. ⑦ Which means a mere 5 tons to the moon per launch.
Which means MANY launches to get a useful payload to a lunar base. Even assuming a railgun return launcher, it's going to be an insanely expensive project to build a moonbase with current launcher technology.
Which leads to the other issue. Return Mass. Figure an LM/CM combination unit for every crewing. It's just within reach of the Falcon Heavy... It's 5 tons, and two men, and not happy. And not carrying supplies. That's a second Falcon Heavy.
Without a mega-rocket like the Saturn V, it's just NOT practical to consider a station. And the political considerations of the Carter Administration basically sealed the doom of manned lunar spaceflight.
Note that SpaceX founder Elon Musk has stated categorically his goal is a manned colony on Mars in his lifetime. He's got the money, the brain-power, and the will. And the heaviest working launch vehicle in the approval process. The question becomes, "Can he get a working colonial craft into orbit, equipped, and staffed?" We can expect the Falcon 9 Heavy will not be the final stage in his ultra-heavy lift needs.
http://en.wikipedia.org/wiki/International_Space_Station Wikipedia — International Space Station.
Didn't need an exact figure, so Wiki's good enough.
http://www.nasa.gov/mission_pages/station/structure/iss_assembly.html NASA ISS Assembly Missions.
http://www.astronautix.com/lvs/saturnv.htm#more Encyclopedia Astronautica - Saturn V
LEO Payload: 118,000 kg (260,000 lb) to a 185 km orbit at 28.00 degrees. Payload: 47,000 kg (103,000 lb) to a translunar trajectory. Success Rate: 100.00%. Launch data is: complete. Development Cost $: 7,439.600 million. Launch Price $: 431.000 million in 1967 dollars in 1966 dollars.
http://www.astronautix.com/craft/apollolm.htm Encyclopedia Astronautica - Lunar Module
http://www.astronautix.com/craft/apollosm.htm Encyclopedia Astronautica - Service Module
http://www.astronautix.com/craft/apollocm.htm Encyclopedia Astronautica - Command Module
http://www.braeunig.us/space/specs/lm.htm Lunar Module
http://www.spacex.com/falcon_heavy.php SpaceX Falcon Heavy page