Competition
No buyer or seller controls the price in an exchange.
Law of demand
As the price of a good or service rises, the people will buy less of that good or service.
Law of supply
As the price of a particular good or service rises, people will produce more of that good.
Equilibrium price
The price buyers and sellers agree a good/service is worth.
Opportunity cost
The internal view of what something is worth. (sacrifice time vs money)
Ex) Not the physical $38 for a box of donuts. It is what the $38 could have gone for instead.