I have just finished my dual green 200mw laser projector, it can do text, graphics, and start to get abit flickery on compicated stuff, but its still awesome for beam shows. In real laser projectors they use special motors called "Galvo's". They are small, but VERY fast and precise motors. Mine are rated for about 20,000 points per second, and cost about $365AU. You then need the laser itself. Depending on the quality of the module you buy, the cost will vary. I have a cheap little 40mw green module, and it is quite hopeless at blanking some complex stuff, then I have a >100mw CNI, which is MUCH better quality, and blanks very well.
If you want to make your own custom animations/text whatever, you will need a thing called a DAC (Digital to Analog Converter). If your on a budget, you can head over to ebay and buy a cheap USB sound card (there is one in a blue box all over the place there, it is IDEAL for the "Sound card DAC"), then u need a amplifier for the sound card, which I can supply for about $40US if interested. Or, an easier way would be to go to pangolin.com and buy a DAC.
Building a laser scanner, especially a professional one is quite costly! I have spent about $1000AU on mine already, and it is far from professional!