The price of one trip to the movies could add to your income and still keep your customers happy.
Income tax.
Wait, come back; I didn't mean to scare you! I just want you to think about it a bit. In particular, think about the way it's paid. For those of us in business, we painfully write checks to the IRS. What about your employees? They're usually expecting a refund check. They don't even think about the fact that the refund is merely the return of their own money - money that the IRS has been hoarding, without interest over the past year. Instead, they view it as a yearly windfall. Why? Because it's painlessly extracted from their checks before they ever get to see it.