Yeah, but that's a one-time cost. Once you build the rig, getting it on site isn't all that expensive, comparatively. And you can relatively easily resupply it,

Yeah, but that's a one-time cost. Once you build the rig, getting it on site isn't all that expensive, comparatively. And you can relatively easily resupply it, repair it, and upgrade it. Whereas a space mining operation requires additional billion-dollar launches every time you need to resupply fuel or parts. Plus, as mentioned above - as far as we know, there isn't anything on the moon of significant primary value.