They need proof that there is usable mineable material for the fuel. If hydrogen is there in quantities, or better yet, water, then we can get into the lunar gravity well and out again.
We need to explore figuring out how to put a sustainable facility like the space station @ one of the Le Grange points as well. Moving from the Lunar gravity well to there with supplies would make anywhere in the solar system a target that could be hit.
But taking everything from Earth up is a losing proposition. Doable if we had to, say to build an asteroid defence of some sort, but would never be sustainable on the Earth economy.
Also small amounts in a continuous fashion can be flung into low Lunar orbit by rail launch, so anything made there could be orbited, then a tug could come down and pluck it up and take it to the Le Grange station. Solar power to about 50000' above the Lunar surface, and powered flight the rest of the way up.
I just don't get the Mars for a man obsession. Once the system described here is working (and has solved all the Mars manned expedition problems) then the Lunar economy will do that expedition, not an Earth bound country.