Actually the FAIR study, and others, did not include a great deal of illegal aliens' costs. Illegal aliens have cost US taxpayers over $1 Trillion per year (net of any taxes they've paid) each year since 2002. It is vastly cheaper to detain and deport every illegal alien than it is to allow them to remain for one year or more.
Actually, it would not be necessary to detain and deport every last one of them. There are ways to make them go home at their expense! There are ways to discourage & dissuade people from violating immigration laws to begin with! It would not cost the US $135 billion to have all immigration-law violators depart or be deported. Announcing a major crackdown on illegal aliens will send about half of them scurrying home within 30 days. It can actually be quite easy to get rid of the majority of immigration-law violators in very short order!

