Supply and demand; the basic concept of economic which tells how many products or service wanted by buyers and how many product or service provided by sellers and buyers willing to pay for. The recent crashed housing market may be good example of the law. When more people join in buying house and the builder can mark the price higher because they control the inventory. They release 5 or 10 houses in a week even they can build 100 houses in a month. More people get the free loan and wants to buy a house continue line up to he door and put their name on the waiting list the demand is higher. The builders can set the price higher each week and people still wants to buy it. Now the price drop because less people buying house and the demand was low. IPod another great example people loves the product and you never see the discount to the IPod Circuit City going out of business and has the sales with big discount on every items they carried but IPod has zero discount. Laws of supply and demand again.Banana is crop and grown in tropical regions which mean most of banana are imported to US. The price of banana will affected by the season and weather that effect the quantity of yield. The other reason is the shipping cost (Banana are imported) base on the gas price and again demand and supple of the cargo space of the ships. Shipping is a seasonal business and the demand of cargo space varies from January to December. Banana is the #1 selling fruit in the world and most favored of American estimated 25 pounds of banana are consumed by a single person in America. Since it is so popular and people will noticed the price change so many grocery chain absorbed some cost to keep the price low in order to bring in customers.