You need to kick the ass of the tire shop. Wait untill they strip one of the heads off a lug that was overtightened and then want to charge YOU extra to get it off.
Better idea. But yourself a $20 torque wrench from Harbor Frieght and check the lugs at random when they work on your tires. If they're over torque, walk right back up front and tell them to do it right.
It's the difference between static and dynamic torque (and if they even set their impact guns for a specific torque). Pay attention to whether they bother changing anything between cars. If not, they're using the same amount of torque to put a F-250 super-duty duelly tire on as they are a Fiesta sub compact. Bad.