Economically speaking everyone pays taxes. Also economically speaking no one pays taxes equally. I would love to see actual statics that show that immigrants do not contribute to local economies at a rate similar to others in a community at a similar pay bracket.

As for supply and demand. I believe the supply and demand of the job market as a whole is exactly what is causing immigration. I believe those market forces will continue to pull in immigration, legally or not. Market forces have a hard time understanding law.