The issue is supply. It's limited. And of those you can't just walk into a store and buy one. You have to be a valued customer. This typically means buying things that aren't watches that have much higher profit margins (since most ADs are jewelers). Or just being a celebrity or high net worth individual.
Compare the Rolex Cosmograph Daytona new for $14,550 MSRP [1] and used (but unworn) for $42,875 [2].