If people start buying $5000 cars here then they will need to make less money because the costing of living will go down a bit.
Now if we let illegal immigrants build houses for $3.00/hour that would really drop the cost of living.
Lets take it a step farther; let illegals work at the companies that manufacture building supplies for example lumber/concrete/drywall/fasteners/etc and then the cost of housing would drop dramatically because the companies would save tons of money on insurance, labor, etc.