After factoring in subsidies and government price controls I don't think it's so cheap anymore.
Yes, the true cost is hidden just like the government's unemployment figures.
Another "cost" that is left out of the equation by the illegal immigrant labor lovers is the crime they bring, they are most likely on food stamps, they use the emergency room as a free health clinic, high teen pregnancy, and on and on.
Not "cheap labor" after all but the farmers get to spread out those costs to the taxpayer instead of paying a real wage out of their own pockets to a lawful citizen.