A basic LCD monitor you buy over the counter is already prepackaged with everything you need to hook up to a common video input jacks such as VGA, RCA, S-Video. The basic components are LCD screen, controller, and backlight inverter. The controller has an input and output. The input connections are either VGA, RCA, or S-Video. The output then connects to the LCD screen. The backlight inverter takes low voltage power like 12v and steps it up to a few hundred or thousand volts for the backlight to light up the LCD. The higher the wattage, the brighter the screen for daytime viewing. That's another story.
Laptop LCDs come with the LCD screen and the backlight inverter and the backlight built in. It does not have a controller. This is the part that most people dont understand why they cant use a laptop LCD. You need a controller to convert standardized VGA, RCA, S-video signal to non standardized LCD signal.
LCD screens dont cost much. You can buy a laptop LCD screen for a few dollars on ebay though they can get as high as $100-$300. The controller is what's gonna cost you the most.