The conservative Heritage Foundation has issued a scathing report against the immigration reform bill proposed by the Senate's "Gang of Eight," arguing that the bill would cost more than $6 trillion -- a claim summarily rejected by Republicans pushing for the bill.

The report states that legalizing current illegal immigrants would cost $9.4 trillion over a lifetime and pay just $3.1 trillion in taxes, resulting in a net cost of $6.3 trillion. And the authors of the study, Robert Rechtor and Jason Richwine, say that's a conservative estimate.