I don't mean to suggest that you don't make a good point. There is no way I would accept less than, say, $10,000 for the promise to sell 100 BTC in five years. It's too risky. But on the buying side, I get uncomfortable at only $100. There is a huge amount of uncertainty. But what about Google stock? It was a positive frenzy at the IPO in 2004, when the first stocks went on sale for $85 per share. Was there ever a more obvious bubble? Yet GOOG trades today at about 1 BTC per share.Bubbles all burst eventually.
If your time horizon extends to the heat death of the universe, then this is undeniable. And it has been true of all traditional commodities I know of. (Tulipomania was a great read.) All investments come to naught on a long enough time scale.