A company released a new video game system just in time for Christmas, and many stores quickly sold out. Although the price of the system was only $350, the game systems sold for over $2,000 on an online auction site. Which of the following economic principles best explains this event?

People respond to incentives because of self-interest.
The value of some objects increases relative to other objects.
The price of all goods will rise over time.
Competition among consumers increases prices.