My thesis work used He3...essentially it does not exist naturally...It comes from the beta decay of tritium. So What I got most likely came from the decay of our tritium stockpiles. It is expensive, $400 for 1 litre at STP. I had to do ~100 of hours of experiments with just 5 litres...

It has potential as a fusion recource, when we develop the tech the price will skyrocket... right now only a _few_ researchers have any use for the stuff, but when it is needed by the 1000's of litres it will be the single most precious commodity by weight than any thing on earth...

I would bet that the worldwide demand for the stuff now is _well_ under a litre a day...10 litres lasted me several years and damn few other researchers would need to use the stuff...I only used it for VERY special reasons... It is pretty much identical to regular helium... except in its mass... and that was important for my work but would not be important for the vast majority of researchers...
In fact it turns out I probably could have used regular He4 but I didnt know that until after I built my experiment.

So what I am getting at is that if we learn to use He3 for fusion it will be worth mining wherever we find it.