Published in the March/April 2007 Journal of Indexes (pages 34-38), John A. Haslem, H. Kent Baker, and David M. Smith analyzed the investment expenses of S&P500 index mutual funds and found a very wide dispersion of management fees and total expense ratios.
Without all their research details, which you can read yourself, Haslem, et. al. simply found that higher expenses just lowered investors' net returns. They grouped S & P 500 index funds by expense groupings from low to high, i.e. standard deviations around the average expense ratio. They reported a list of twenty-five retail and institutional index mutual funds with lower costs.