The cost of investing in the S&P 500 index fund varies depending on the specific fund and brokerage firm used. Generally, investing in the S&P 500 is considered low cost compared to other investments, with expense ratios ranging from 0.03% to 0.5% or more. Other fees may apply, so it's important to carefully review the fee schedule. This means that for every $10,000 invested, the annual management fee would be between $3 and $50 or more.