Three exchange-traded funds (ETFs) - Birla SL Nifty ETF, HDFC Nifty ETF and ICICI Pru Nifty ETF -- are probably the cheapest equity mutual funds currently available in the market. These largecap ETFs have an expense ratio of only 0.05 per cent. ETFs are supposed to be cheap as they are passively managed funds that primarily track their benchmark index.