It doesn't cost much to maintain the peg. In fact, it generates gains for the fund. If you think about it, when the price of HBD is low, the fund buys more to raise the price. When the price of HBD is high, the fund sells to lower the price. It is always buying low and selling high. The act of maintaining the peg is profitable with ordinary market fluctuations. Prolonged dips or rises could be a problem. But savvy Hivers will also jump in to profit, which assists the fund.