I think that's been answered. He may just be sanding for RIDS, but *if* he is sanding the entire car down to remove orange peel than the price isn't completely ridiculous. High? Yes. Stupidly high? No.
Let's look at it like this (sorry if I am playing devils advocate), but on say, a Carrera GT (a $400k car used), you're probably talking about 80-100 hours of work. Now that's anywhere from $80-$100/hr, which is a lot, but on a car of that value I can sort of understand. I wouldn't charge that much, but $80-$100 hour isn't a lot more than what a lot of detailers on here charge, and it's less than body work, which this is kind of akin to.
Of course it is possible he is just sanding RIDS, in fact I think that may just be the case, and the cost is largely based on his skill *plus* his reputation, which is a different story. No less justified (imo), but different.
One more thing; as toyotaguy mentioned it isn't like this is what he is doing every day. I've had details where I charged close to this price, but for me that's a once a year thing. I don't advertise that on my site, he does, that's really the only difference.