These guys spend absolute fortunes - millions in many cases, on R&D, cutting edge technology, proximity hosting, hiring smart cookies etc etc. The high frequency shops look upon roundtrip times to the relevant exchange etc in terms of milliseconds.
Some really good points were made, one of which was that all these strategies, and any edge they may generate, are basically a decaying asset. So there's a delicate balance to be surfed by these firms between R+D speed, amount of forward and backtesting, how much time and effort they put into operational factors etc.
Bottom line is - the systems stuff we see here on this site is really truly the tip of the iceberg compared to what else is going on (and while the thing I went to recently was pretty heavily dominated by high frequency traing shops, they were by no means the only people there. Plenty of macro quant funds too). And at the pro level the money and resources thrown at this stuff is unreal. Which is all the more reason to have a realistic view of what can be achieved with a small scale mechanical system.
Not to say that no-one will ever make money doing that, it's just that if there truly were a quickfix shortcut to riches, don't you think people might have thought about it by now on the wholesale side? Like em or hate em (and there are people on this ste who REALLY have the wholesale community in pretty low regard as far as I can tell), they're certainly not all stupid.