Going rate (and recs) for a building surveyor

As part of our project to raise the penthouse roof a few feet, our architect needs detailed elevation information for our current roof (7th floor in Flatiron). The first quote came in at $2,800, which was more than double what we expect. We are planning on getting some more quotes, but does that seem reasonable? The building is about 40′ wide and 70′ deep.