I got my oil changed today. One of the guys there sits down and says that he'll put the more expensive oil I selected in my car while charging me for the cheaper stuff (about 60%) cheaper. The catch is he wanted me to give him a half the difference in cash under the table as a gratuity.
I told him that I wasn't comfortable with that arrangement. He slunk off.
He came back later and claimed even a preacher the other day had taken the offer. In that case? Still, no. He then proceeded to tell me that when I bought the car, someone made a profit. Well, yeah, but that was built into the structure of the business model. What he wanted is make money under the table.
See, while its good for me (I get it cheaper) and good for him (he gets cash under the table), its not so good for the company where he works. He will get caught eventually. I know too many people who have done the same and gotten fired.