Was there any government overseer looking over the shoulder of you or the cashier making sure everything was "fair"? Of course not. Many will say that these transactions happen "in the shadow of an overseeing government" and that is why people behave in a fair manner, which is really not true. People behave this way because there are social checks against bad behavior.
In the following video, Professor Peter Leeson speaks about anarchy, both the underlying, invisible anarchy of our daily lives, as well as the well regulated sort that has been in place ever since wooden ships circled the globe.
One quibble, when Professor Leeson speaks of having dinner and not making a "contract", I find that his premise is off when he says a contract was not made. As a proud student of Dr. Art Stowers, as well as Dr. Allen Reagle, for my University of Tennessee Business Law courses, I am here to tell you that you made a contract every time you made a transaction. If it is unwritten, it is a verbal contract even if no verbals were exchanged.
Professor Leeson does continue with his example and ask the audience if they have ever taken a restaurant owner to court over anything and the answer was no, primarily because the costs of going to court over the wrong order are so much greater than merely telling others of their bad experience and not returning.
Don't take my sometimes inaccurate memory for it, take a look at what the experts have to say:
In the United States, verbal contracts will usually refer to unwritten or oral contracts. An unwritten contract will usually mean that the contract or agreement was made through the use of spoken words as opposed to formally writing and entering into record the provisions of said contract.What we usually deal with in our everyday lives is the anarchy of self governance. Far from a chaotic situation, it is a situation of order brought through customs evolved over the centuries.
Simple Guide to Verbal Contracts - Laws.Com