That theory relies entirely on the supply side. But what about the demand side? Without accounting for both you know nothing about the price of something traded

That theory relies entirely on the supply side. But what about the demand side? Without accounting for both you know nothing about the price of something traded on a market. What if next year some other cool new "currency" comes along and no one wants your stinkin' bitcoins any longer? Does it matter that supply has a cap? No. It matters as little as the limited supply of paintings created by some forever unknown artist.