It is the fundamental framework of economics. In its simplest form, this is what economics looks like. The social science of human interaction, and the transfer of wealth through those interactions. All condensed into one word. One, eight-letter word.
Scarcity.
In a world with scarce resources, economists must weigh the opportunity costs of every decision. They must recognize the trade-offs that they face, and they must think at the margins with every decision that they encounter. Within reason.
It is for this reason that self-interest pervades in the economy, and in the National Football League as well.