what is there ain t no such thing as a free lunch tanstaafl 
 there ain t no such thing as a free lunch tanstaafl also known as there is no such thing as a free lunch tinstaafl is an expression that describes the cost of decision making and consumption the expression conveys the idea that things appearing free always have some cost paid by somebody or that nothing in life is truly free a free lunch refers to a situation where there is no cost incurred by the individual receiving the goods or services being provided but economists point out that even if something were truly free there is an opportunity cost in what is not taken 