Paid Coffee & Free Coffee

Once a conversation was going on between a customer and a waiter in a hotel.

Customer: Dear waiter, everyday you charge me for a cup of coffee. Don't you think, it would be damn wonderful if you serve me coffee free of cost today?...

Waiter: Dear Sir, I totally agree with you. Everyday, you drink from a cup filled with coffee. Indeed, it would be really wonderful if you drink coffee from an empty cup today.

Customer:!!!!!