When I got started in training, the pencil-type laser pointer was over $100. Needless to say, I found other ways to point at the screen (hand shadows being the primary one).
Recently, I finally broke down and got a laser pointer, which I keep in my trainer kit. The cost? Only $3, in a clearance bin at Walgreens. It was sold as a cat toy: a way to put a spot of light on the wall for cats to chase around. (It also puts up an image of a mouse, a butterfly, a star, and my favorite, a smiley face.)
The use of laser diodes in mass-market equipment such as CD and DVD players has lowered their production cost so far that now they can be sold as toys, not $100 professional tools. I don't care what it says on the package, it's a dandy training aid.
On the other hand, training is often compared to herding cats, so maybe the package description is appropriate.
NOTE: Do not put this in your carry-on luggage. It's considered a weapon and forbidden by the TSA, so pack it with your trainer kit in your checked luggage.
UPDATE 2/4/2011: Laser pointers no longer appear on the TSA's list of prohibited items, and haven't for some time. Thanks to reader LaserPointers for asking me to research and update this post.