There are other costs to consider besides Transaction Costs
My friend Sheyna Steiner over at Bankrate.com wrote an excellent article about No-Fee ETFs. These are funds that can be traded without transaction costs. The transaction cost is the amount you need to pay to buy or sell the fund. For example Scottrade charges $7/trade, Charles Schwab charges $8.95/trade, and E-Trade charges $7.99/trade . While avoiding costs is always a good thing there are other factors to consider - I was able to help her out with some thoughts on these unique investments.
I gave an example to show how a bid/ask spread could become very expensive for you.
Ultimately, the investments are only the tool for accomplishing your goals. If you can save on costs all the better, but you should place greater emphasis on your plan.
Or check out our earlier article of the full cost of investing in exchange traded funds and mutual funds to better understand your total costs of investing in any mutual fund or exchange traded funds (ETF).