Exactly. If economic growth was just like microbe growth in a petri dish, sure, a simple equation would suffice. But people choose and act based on their own thoughts, opinions, and goals, and they are always readjusting to new input and information. Economics can tell us reliably that if you add supply, you press the price downward. What economics can't tell you is what crazy and amazing things the humans will do in response to that.
A good historical parallel for this kind of situation might be aluminum, which was a precious metal for many years. When it suddenly became available in large quantities due to new chemical processes for extracting it, supply skyrocketed and led to whole new industries. I don't think anyone in 1890 could have guessed what the ultimate demand for aluminum would settle at, even though it was clear the price was dropping precipitously.