I dated a landscape architect at one time. I about choked when he showed me one of his recent projects and told me what it had cost. He did some jobs around new builds and some businesses that were in the $50,000-$100,000 range. That was about 15 years ago.
Landscaping is not cheap. That's why my yard looks really crappy. I can't afford to hire someone and I don't have the skills myself. Ask around for other quotes but I'm guessing they will be similar. The "labor" costs cover not only the time that goes into the job but also the upkeep of the equipment used and the planning and design time. If the ground is rocky, sandy, or clay based there may need to be extra steps taken as well.
Is the quote you got reasonable? Probably, but different areas of the country will have different rates.