They pump far more than that into the economy in terms of labor. And that is a minor disaster for the Mexican economy. The "23 million Mexicans" (I find it more than a little annoying that they're calling 13.5 million Americans "Mexican", but that's another story...) in the US are adding to our economy, not theirs. The $9 billion they get back is hardly compensation for the economic activity that stays north of the border.
Because of their much lower education levels, Mexican immigrants earn significantly less than natives on average. This results in lower average tax payments and heavier use of means-tested programs. Based on estimates developed by the National Academy of Sciences for immigrants by age and education at arrival, the lifetime fiscal impact (taxes paid minus services used) for the average adult Mexican immigrant is a negative $55,200.
Incorrecto, senor!
According to Mexican government's own statistics, the AVERAGE Mexican immigrant to the US has only a 7th grade education. In other words, half have LESS. These unskilled workers add NOTHING to our economy. They make big fat profits for employers like Tyson who abuse them, but that is only because the employers dump the social costs on the American taxpayer. In California, it's estimated that each immigrant costs state $2K+ per year in education, healthcare, roads, policing, social services, not to mention pollution, traffic congestion, higher crime, higher housing costs, lower standard of living...
The calculated efforts by the Republicrat and Demopublican elites to Hispanify America is simply a plan to redistribute wealth from the middle class (workers) to the upper class (investors).