That doesn't matter. If you sell a contract for August now, the buyer of the contract is the person who has to worry about the price of the contract going down.

That doesn't matter. If you sell a contract for August now, the buyer of the contract is the person who has to worry about the price of the contract going down. As the seller, you just have to deliver the goods as specified by the contract. You've already been paid. The relevant missing fact here is that the 300% ROI ignores the cost to operate a supertanker.