well a quick look on ebay shows 50mW green l@zers available for around £20 and 2-300mW l@zers for around £100 - £150.
The latter are classed IIIB, and according to wikipedia "l@zers in this class may cause damage if the beam enters the eye directly... l@zers in this category can cause permanent eye damage with exposures of 1/100th of a second or less depending on the strength of the l@zer. A diffuse reflection is generally not hazardous but specular reflections can be just as dangerous as direct exposures. Protective eyewear is recommended when direct beam viewing of Class IIIb l@zer may occur. l@zers at the high power end of this class may also present a fire hazard and can lightly burn skin."
Now if some little s**t shines one of those in my eyes when I'm flying I'm not gonna be happy!