The clip shows a good example of the double coincidence of wants and how a barter system is difficult to maintain. The seller of bread needs somebody to take care of his kids and the guy who can take care of his kids wants extra bread. They need what the other has and have what the other wants. The trouble is determining how much work is appropriate to get a loaf of bread and then managing the system to make sure everyone gets paid.
Thanks to Mathew Abraham for the suggestion