It's difficult to say which ETFs are the most "expensive," because that term is subjective when it comes to investments. An opportunity may seem cheap to one investor and expensive to another, and there may be times when it's difficult to say who is more correct. One common way to evaluate whether an ETF is cheap or expensive is to consider measurements like the price-to-earnings ratio. When considered in context with the rest of the business fundamentals, these measurements can help investors more accurately compare the values of investments.