Ballmer probably knows it's his last executive position he'll ever get in this industry. So he's squeezing as much out of it as he can. Or he's just a fanboy of the "old Microsoft."
It's the same drive that everyone has, to progress in their life. They see the money as a way to count up all their successes. Not an unheard of algorithm. Not my personal one but not unusual.
Ballmer is so rich and so old, he couldn't event spend it if he wanted to. This is really unlikely.
Have you seen his office, it's not about the money.
The two things are not always mutually exclusive. Society generally associates money with success. Thus money is the benchmark for ones ego.
Not just with CEOs as either. I often read online comments from warring zealots who proclaim "I get paid a i to do this stuff!", as if it somehow validates their claims.
