From an editorial by Darrell West on CNN.com:
It is time for candidates and political leaders to tell the real story about immigration. Even though illegal immigrants enrage many Americans, it would be prohibitively expensive to deport 11 million people. As a vivid illustration of this point, the Center for American Progress found that mass deportations would cost $285 billion over five years, or an average of $900 for every American.
If people actually are worried about government cost, they should support the creation of a pathway to citizenship based on paying back taxes, learning English and collection of a serious fine for illegal entry. Experts say that a full path to legalization would add $1.5 trillion to the American economy over the next decade. It would be cheaper to legalize illegal immigrants than keep them underground and outside the mainstream economy.