I think I understand. The profit is determined by how much the spot price has increased during the term, since the futures are bought for the spot price at the beginning of the term and sold for the spot price at the end. Put that way, this looks much more like all the other bubbles we've read about.

I get the feeling that there's really only one bubble, but it moves from one sector of the economy to the next, leaving destruction in its wake, kind of like Bugs Bunny used to tear up the ground as he burrowed through it.