Surely the pioneers in this business would be well aware of that fact, and would presumably control the supply. Although the goal is ultimately to lower prices

Surely the pioneers in this business would be well aware of that fact, and would presumably control the supply. Although the goal is ultimately to lower prices and make these elements ubiquitous, the transition wouldn't happen overnight. It's likely that logistical limits in transporting the material back to Earth would be enough to avoid crashing the markets.