They are making a killing, they just don't talk about it. I know several people who are doing this. Currency trading, predicting dog & horse races, options trading - all one man shows with a tiny little grasp that nobody else has. Each making a couple million a year trying to figure out the next little trick (all the straightforward tricks are owned by Goldman's super fast computers). More than once I have seen 1 second of lag cost them big, but overall they are maxing out the opportunities their little (< 20k loc, usually in vb of all things, sometimes in python or ruby) stats programs have found.
Furthermore, I work as a business intelligence quant for the online tech space. I've DRASTICALLY increased ROI rates for online ads, as well as conversion metrics, with my formulas and clustering models. There is so much low hanging fruit out there it is crazy.
If anyone wants to get into this field I'd be more than happy to point you in the right direction.