Get back to me on 3He fuel mining in the regolith after (a) demonstrating a working 3He cycle aneutronic fusion reactor (hint: it's much harder than the D-T fusion cycle that we haven't got working yet, although ITER is supposed to demonstrate it), and (b) ruling out other aneutronic fusion fuels like, oh, proton-Lithium-7, or proton-Boron-11 ... which are only somewhat harder to achieve than 3He fusion, and which run on fuels readily available here on Earth.

(My gut sense is that if aneutronic fusion is practical at all then it'll be cheaper to build more expensive reactors that can run on terrestrial fuels so cheap we use them for car batteries and as an insecticide, rather than slightly less difficult reactors that are fuelled by magic extraterrestrial unicorn sparkle-dust.)

Helium-3 from the moon will never be a commercially viable energy source. At best it might be captured incidentally as part of other mining operations and sold to research labs. There are just too many other fusion options that, while not as ideal, have fuels that are vastly easier to obtain.

It is likely that permanent low gravity will kill them even before boredom and depression from realization that the rest of their lives will have to be spent in those small confines.

(Low gravity is extremely unhealthy. And even a relatively short 1-week stay in such conditions severely affects cardio muscles, so that super-healthy astronauts have to exercise for several hours per day to keep their heart in shape)

Fusion power plants already seem unlikely to be economically viable, given the huge radiation damage that the whole structure takes, requiring constant disposal of radioactive concrete (presumably via robots) and rebuilding the structure every 10 or so years. Adding lunar-mined fuel to the process seems to be going in the wrong direction.

70 wealthy retirees, each paying $100M annually.