How much is a tuba?

Gene called me after picking Austin up from school when they were on their way home. Austin said in the background, "I want to talk to her." Gene handed him the phone and we talked about his day. I asked him what kind of ice cream he had at school and he told me he didn't push or hit anyone today. (Austin's had a bit of trouble with keeping his hands to himself lately.)

All of a sudden he asked me, "Mommy, how much money do I need to buy a tuba?" I told him that I didn't know, maybe $20. He said, "Yeah, $20." I asked him if he had $20 in his piggy bank at home. He said, "We'll look."