Janna, this is so much like my son. This is exactly how he relates to those around him. He's always the comedian (but not really funny). I have gotten him involved in drama (drama camps, plays, small town drama groups, he had a part in the Middle School play and was fabulous) and he's totally excelled. I've tried to find an outlet for his ability to "perform". I just really didn't know what else to do other than find something positive to throw into the mix. He knows he's not supposed to do it during times when others have the floor (teachers, etc.) so he has always (well since about second or third grade...4th grade was really hard) gotten the negatives for it. It's part of him though and it's always been part...he just pushes it too far (which is classic it seems).
It's not motivational though with- him like you described in your son (you told him about the money thing and he stopped). My son can't do that. I mean you can take whatever or give whatever and it doesn't help him. He learns quite differently. He's very smart and for awhile I just thought he was bored but that's not it...it's probably some form of ADHD.
When we saw Greene, he asked me about ADHD and I told him that he could attend to things he was interested in for long periods of time. Greene said that sure many kids with- ADHD could do that, the test is whether they can attend when they don't want to because kids with-o ADHD can do this for long periods as well (attend even when they don't want to). That's why the squishy ball came in handy...it gave him something to do to help attend. Not that it would help your son, but it did help mine and still does here when he's needing to listen to things that he'd probably rather not.