A little old lady sold pretzels on a street corner for 25 cents each. Every day a young man would leave his office building at lunch time and, as he passed her pretzel stand, he would leave her a quarter, but would never take a pretzel.
This went on for more than five years. The two of them never spoke. One day as the man passed the old lady's pretzel stand and left his quarter as usual, the pretzel woman spoke to him, "Sir, I appreciate your business. You are a good customer, but I have to tell you that the pretzel price has increased to 35 cents."