[gull]

Let me clarify:

Periodic investing is fine. Investing 10% of your paycheck each month is a great thing to do.

By dollar cost averaging, I'm talking periodically investing some amount of money that you already have. The reason it's bad isn't because of transaction costs - it's because the money you have in the market has a positive expectation, and by dollar cost averaging, you're not getting the maximum return because not all of the money is invested.