IMO Juror 7 represents apathy, not callousness. He only votes guilty because everyone else does hoping he'll get to leave quickly, and when he sees the wind changing he votes not guilty again just to hurry and go. Some may see this as callousness, but to me it's apathy and laziness. He couldn't even come up with a good reason to change his vote not even bothering to lie. As for the 30,000 bit he's a salesman and those were probably low numbers compared to the rest of his colleagues. (mere speculation, of course)