I was just talking to the husband about this the other day! I don't have a 3D printer of my own and I don't have access to one, but all the little trimming tools and such that I now make out of cardboard and tape, I would make to my exact specifications with a 3D printer.
Cost-effective or not, if I taught classes (or was a shop) I'd make some little widgets that helped that specific project and include it with the class, along with my advertising info on it.
A friend of a friend is an ex-Boeing engineer and does work with kids and the competition robots, he was the first person I knew who had a 3D printer and they had just came out.