It might be typical of a dealer price, but there is no way it is fair.
The clutch master is much more difficult to replace. Maybe $500-ish for the master is closer to fair. But I think replacing the slave shouldn't cost more than $300 or so, assuming 90 minutes of labor.
But the slave is easy to replace.
1. Buy $100 for the part itself from Del Ray Acura. Order an o-ring too.
2. Remove airbox (~5 minutes)
3. Unscrew clutch fluid line from old slave cylinder, catch draining fluid somehow
4. Remove old slave cylinder.
5. Grease end of new slave. Re-mount.
6. Replace o-ring on fitting.
7. Re-attach fluid line.
8. Bleed line.
If I lived where you do, I wouldn't be taking my NSX to the dealer. I would be taking it to this guy. Most experienced NSX mechanic in the NY-NJ area, prices are always fair, etc. And he's only 40 miles away. You're a lucky guy!
A quick second on nsxtasy's recommendation of a service provider for your NSX. Larry is without doubt one, if not the most, knowledgeable person anywhere concerning the NSX.
I trailered my car to him for TB/WP 60K mile service and it was the second best thing I ever did. The first being buying my NSX. I HIGHLY recommend him. Plus he is a cool guy.
I'm in touch with Larry now, so he'll likely do all future work on the car. The car only has 20k miles and only had oil and brake fluid changes, so I felt comfortable with the dealership doing the work.