IIRC, it takes just as much energy to reach L4 (or L5) as to reach the Moon--they're in the same orbit. If you've got settlers on the Moon, or beyond the Earth

IIRC, it takes just as much energy to reach L4 (or L5) as to reach the Moon--they're in the same orbit. If you've got settlers on the Moon, or beyond the Earth-Moon system, L4 is probably a good place to build a commercial and industrial outpost; but, for your only space installation, something lower down is much cheaper.