These statistics are taken from the Bureau of Labor Statistics' Occupational Outlook Handbook 2002-03 Edition.

"Many experienced technicians employed by automotive dealers and independent repair shops receive a commission related to the labor cost charged to the customer.  Under this method, weekly earnings depend on the amount of work completed.  Employers frequently guarantee commissioned mechanics and technicians a minimum weekly salary.  Many master technicians earn from $70,000 to $100,000 annually."  Bureau of Labor Statistics