Ah yes, index mutual funds. They do have fairly low MERs. In Canada, their ETFs are not as low as broad market ETFs, but fairly low.The Fidelity 500 Index fund has an expense ratio of 0.015%. Even the Vanguard index 500 fund has a higher expense ratio at 0.04%. But if you look at the expense ratios of the index 500 funds for ETFs, they're higher. Probably because the total assets in the funds are much lower than in Fidelity or Vanguard.
https://fundresearch.fidelity.com/mutual-funds/summary/315911750
https://investor.vanguard.com/mutual-funds/profile/VFIAX
In Canada, the MERs of "regular" (ie managed) mutual funds are much higher than broad market ETFs, 10 or 20 times as high or higher.