Which is the least expensive type of doumbek?

My son has said that he would like to learn how to play the doumbek. He tends to choose new hobbies regularly, and only sticks with a few of the different things he tries out, so I want to start him off with an inexpensive doumbek until I know whether or not he will continue to play. Is the aluminum doumbek the least expensive? A store near us has one of these, and I was thinking I might get it for him for his birthday next month. I will need to help him find some lessons as well I suppose.