While ETFs have a low expense ratio, they do have some charges that are specific to them. Because ETFs, like stocks, are purchased as shares through a broker, an investor must pay a brokerage commission each time he or she makes a purchase. In addition, an investor may incur the standard fees of stock trading, such as disparities in the ask-bid spread and so on. Traditional mutual fund investors, on the other hand, are indirectly susceptible to the same trading charges because the fund pays for them.