By demanding automation, HFT drives down the operational cost of a particular transaction. However, for trades themselves, it's arguable that it drives up the cost of the overall transaction for long-term traders - especially those who end up needing to break up a larger overall stock transactions into smaller batches.
I find it hard to believe the overhead of doing that comes to more than $.24/share.
It does mean the market demands more knowledge; it's more sensitive now, so you can no longer do a buy or sell "at market" and expect a good price. But even if you don't know how to play the market you can go through a broker and still pay far less than you would've in the "good old days".
