That's not so much an issue with grain prices. Rice and bread and such are the most basic of staple foods, and pricing people out of that market results in hunger and starvation.
The article mentions that it would be better if some of the farmers started growing vegetables rather than grain, but the subsidies don't pay for vegetables.
Same for wheat - low gluten types are cheaper. (Which is basically why they invented the http://en.wikipedia.org/wiki/Chorleywood_bread_process )