Sorry, a little off topic, but did  Satoshi really say that? Everything else I see from him has been clear-thinking and concise, but this gets things backwards. It's not that the price of the commodity gravitates towards the (current) production cost so much as the reverse, at least in the case of a commodity like bitcoin. If it costs $200 to produce a bitcoin that sells for $300, then rational investors will buy up more mining equipment to earn that profit. But more miners means divvying up the (fixed rate of supply) bitcoins more, leading to increased production costs per bitcoin.

In principle this would continue until it cost as much to produce a bitcoin as it sold for, accounting for all costs (electricity, personnel, etc.), on average. Of course with the volatility of BTC and the time lag involved in ordering and setting up miners, the relationship has been very loose. But over the long haul it should hold true.