The extraction process is a lot more costly. It involves...

The extraction process is a lot more costly. It involves roasting and leaching with water. Majority of studies I have read (different temps, different loads ect) achieve a 50% extraction, but I have seen some as high as 90%. Most of these used a 2.5%+ Li sample.

Even with large increases in demand, I don't think the lepidolite option will be used in any major way anytime soon. Plenty of easier/cost effective options available. The market certainty wouldn't take to the idea well anyway.