Things to know about ICs... (from Wikipedia)

"There are two main advantages of ICs over discrete circuits: cost and performance. Cost is low because the chips, with all their components, are printed as a unit by photolithography rather than being constructed one transistor at a time. Furthermore, much less material is used to construct a packaged IC die than to construct a discrete circuit. Performance is high because the components switch quickly and consume little power (compared to their discrete counterparts) as a result of the small size and close proximity of the components. As of 2006, typical chip areas range from a few square millimeters to around 350 mm², with up to 1 million transistors per mm²."