Nice instructable on how to take the motor with gears out of a cordless drill. Yeah 15-20 dollars for the drill isn’t cheap. But if you look at buying the motor with gears from a hobby shop (60 up) its cheap. Not to mention you can sometimes get used cordless drills cheap or free after the batteries are worn out from folks.
http://www.instructables.com/id/Hacking-Drills-CheapPowerful-GearboxMotors-for-/