I saw a blog calculate that regolith He3 was so sparse that even with a reactor to use it in, one would make more energy from purifying the metals, coil-gunning the purified ingots just past the L1 point so they would fall to Earth, and setting fire to the ingots. Or, entirely separately, by pointing the ingots at electromagnets and collecting the energy from the induced currents from electromagnetic braking.

(I wish I could find the original and link to it. For all I remember it might have been you who wrote it).