Did the accountant teach the old man a lesson?

An old man was selling watermelons. 

His price list reads: 1 for £3 or 3 for £10. 

A young accountant stops by and buys three watermelons, one by one, paying £3 for each. 

As the young accountant walks away, he turns around, grins, and says, "Hey old man, do you realise I just bought three watermelons for only £9? Maybe business is not your thing." 

The old man smiles and mumbles to himself, "People are funny. Every time they buy three watermelons instead of one, yet they keep trying to teach ME how to do business." 

The young accountant heard what the old man said and vowed to never again be so arrogant or stupid. 

He went on to run his own practice and never forgot his watermelon lesson. 

Listen to your clients for they may well know more about their business than you do.