And the crazy expensive switch is guaranteed to be the cheap part. Now add the all the ip required to make that fpga smart enough to place orders, and you're talking huge bills in dev hours and third party licensing.
http://www.bittware.com/fpga-dsp-applications/applications-s...
Want to work in that field? Know VHDL/Verilog, Linux, networking down to the wire level?
The "serious dough" part is a little harder to quantify. I've not looked into NASDAQ specifically but server colocation is usually on the order of a couple of thousand dollars a month. This is a drop in the bucket compared to the real costs of a professional trading outfit (namely employees and margin/risk costs).
Anecdotally, it's also almost exactly what I paid for a tier 1 co-located server at my first job in a startup during the first dotcom boom.