Traders having made their bundle, oil drops 9% in 4 days, dollar rebounds a little

[Acer]

Many speculators make their money on the change in the market price, not on the commodity actually being purchased. As long as they can time it to sell higher than they bought, they have succeeded. This adds to the pool of money chasing after the commodity, and for a time the price rises counter to the supply...for a while. Of course, having more money available helps this, but speculators speculate in any market.