Sorry, the numbers just don't add up.
Don't know where these figures come from, but to arrive at this $500 billion, one would have to "assume" that EVERY single one of the 12,000,000 Illegal Aliens, was working; earning an average of $12,500 a year for ALL of the 22 years, and they were ALL getting paid in the customary manner and had Income/SS taxes withheld.
I think the key word here is immigrant- it seems like they lumped illegal aliens and legal immigrants together to arrive at this number. Many citizens of other countries who are working and living here legally hold high paying jobs. Not sure, but that is the only way I can see that their numbers could possibly be true.