Supply and demand for any commodity are never going to align perfectly - like a pendulum, they will move in either direction. Orocobre had a good run getting high prices, that might be over for now, but the important fact is that they are a low cost producer. Ionce invested in gold at the wrong time just before a big price drop for the commodity, and I invested in a high cost producer. It was a lesson well-learned.
The other thought I have is that while we can make short term predictions on lithium demand, this is a new area of production ramping up for as yet unknown future demand. What will the demand be for electric vehicles? Energy storage? There are probably a lot of new uses and products that are as yet not even developed that will support the demand side for a long time.
We don't know what we can't know. Investing in lithium is a gamble, but I think the odds are stacked in its favour as a long term investment.