Re: business case
(it is the optimal fuel for fusion reactors, but very rare on Earth)
Deuterium-helium-3 has a reaction cross-section several orders of magnitude lower than deuterium-tritium at temperatures that current reactors can easily obtain, and only briefly approaches D-T's reaction rate at ~5-10 billion kelvin. This makes it less than optimal for near-term fusion hardware.
Regarding a base on the moon to fuel hypothetical fusion reactors, it's worth noting that helium-3 is the decay product of tritium, which has a 12.5-year half life. I'm willing to bet you can brew up helium-3 from dedicated tritium generators (high energy neutron or proton sources to bombard lithium, boron, or magnesium, like fusion and fission reactors, or a proton accelerator) for less money than operating a moon base. Even deuterium-helium-3 reactors will have a substantial neutron flux from their deuterium-deuterium side reactions, so they might breed their own fuel from a lithium blanket.