While what you say is legitimate do you really think it stops there?
The last time you had your house roofed did you ask the roofing company that gave the quote if they employed illegal aliens? Or did you just go with the lowest price?
Roofing companies who don't hire cheap labor cease to exist, its as simple as that.
Start fining roofing companies (and any other employer) that break the law by hiring illegals and see how quickly the situation changes. If it's all about cheap labor then why not hire children? Oh, yeah--it's illegal. Not only that, but the government actually enforces that law, so employers actually abide by it.
I had my roof repaired recently....and I sought quotes from several sources. The most expensive was clearly going to be the cadillac job. The least expensive quote I received was from a crew in a beater truck, and the crew members maybe had a complete set of teeth amongst them...but no one had all of his teeth.
I didn't choose them, even though they were the cheapest because the obviously were not going to be around when or if the roof started to leak in 2 months....
I didn't choose the most expensive either...but rather went with a company that has been in business for a long time, and was moderately priced.
Price alone doesn't sell the job.......and the prudent will think beyond price, and look at value.