When it comes to investing, you cant predict the future. What you can predict, with 100% certainty, is how much your broker is going to charge to get you there. If youre like me, the majority of your stock market investments are in mutual funds in retirement accounts like 401(k)s, 403(b)s, and IRAs. While we cant control how they will perform, we can be smart about where we invest by picking good funds with reasonable costs.

In this video, I look at some index funds, the easiest type of fund to compare, and how picking a low cost one can make a huge difference in your retirement nest egg.

The expensive S&P index fund cited in the video is the Rydex S&P 500 (RYSYX ) with an expense ratio of 2.28% and a deferred sales load of 1.00%. The cheapest funds, I mentioned Schwab (SWPPX ), Fidelity (FSMKX ), and Vanguard (VFINX ), are all listed on my cheapest S&P 500 index fund.

One final note, all index funds are not created equal. Could it be that Rydex is giving something extra for an expense ratio ten times greater than the big brokers? No.

This post is part of the Bargaineering Annual Financial Review week series where we take a closer look at the four major facets of personal finance and see if we can do better. This post is part of day three – taking a closer look at your investments.

Despite Rydexs much higher expense ratio, you dont get much for it. If you look at this screenshot of Morningstars Fund Comparison tool. the returns arent exactly equal. The YTD Return (%) figure on the table already accounts for the expense ratios (which is why the Rydex YTD is so much lower).

After you compare pre-expense ratio YTD returns, Rydex beats the three others by less than a quarter of a percent. Oh, and the YTD doesnt include the 1.00% deferred sales load or the fact that they are Class C shares .

To put the expense ratio into perspective, none of the funds on Money Magazines list of the 70 best mutual funds of 2009 has an expense ratio over 1.50%, which include actively managed funds.

Research your funds, it could cost you hundreds of thousands of dollars.

Finally, big thanks to Intuit and TurboTax for supporting Bargaineering and sponsoring this video. If youre on Twitter, I invite you to follow @TurboTax for more information on tax and product news straight from the experts.