I purchase things on sale. When consumers do not purchase items because they are either unwanted or unneeded, the demand for that item is down. The store will want to either make room for a new product or one that is selling better. They mark it to the right price to sell fast and BAM, it's bought!
On the other hand, if there is a high demand for a product the asking price may go up and a short supply can actually cause prices to continue to increase such as gasoline. When the price goes down, usually it is because there is a larger supply all of the sudden or the demand has gone down enough to warrant a lower price.
