Watch the movie "national treasure"...the main character uses a very long and drawn out method of copying someone's finger prints and using them to open a door.
While this method is pure Holllywood, a simpler and slightly easier way can be used to pick up someone's finger prints and simply copy them. So for a very cheap finger print scanner, it can be fooled in a matter of minutes with a dusting kit and some other supplies.
I wouldn't buy one personally just for security unless it was a very good quality. But just for fun sure i'd like one.