Yeah duncans are pretty pricey, but seem to vary from store to store.
Funny story, there's a local pet store here that doesn't specialize in fish, but they have a couple tanks of saltwater stuff. Unfortunately, most of their stuff is pretty unhealthy looking and no one that works there knows anything about saltwater, so I don't shop there, but if I'm in the area, I'll stop by and check things out.
Over the weekend, they had a colony of duncans (at least 10 heads) mismarked as an elegance coral and priced at $90. I laughed, but didn't have the money to buy it.