You're not getting the point.
Illegals enter the country between their teens to thirties. No fixed costs of youth to raise them (non-productive years, don't produce, only consume). Due to illegal status, they pay taxes but can't collect refunds (loophole:cash economy, nothing to do about that) Then they have babies which are now american citizens and entitled to school, SCHIPs, free lunches and govt. aid until 18, whence they enter the workforce and pay : Social Security, Medicare/mediaid, and federal taxes. For the next 40 -50 years, unless they work the system (many do), they pay in and get really very little out. Also keeps wages on the lower end low and workers mobile.
To maintain a growth economy, you have to have growth. Growth in demographics and population number is a real effect. How do you think there is going to be growth in the economy without population growth? That's called JAPAN - no growth there for 20 years and the sun seems to be setting there for ever - cultural xenophobia precludes immigration. Europe too, less acute and sooner along the curve than that.
As long as these folks pay in more than they get out, I don't have a problem with them cost shifting onto the health care industry. I'll profit on the back end selling my high end home to a 2nd generation immigrant which is his family's first success story gaining access to the professional and managerial classes.
Educated professionals come in through H1B's and stay. Physically adept and plucky souls through the rio grande.
The real hurt, I suspect, is when scores of these folks leave for their own countries along with their wealth breaking the expectations of them paying into the system and receiving nothing for it. It happened recently in 2007-2008. I don't know if anyone smarter has looked at the implications of this. Maybe they should.