Not sure about mark up. I do know that Nightforce closely controls the pricing of their scopes and tries very hard to make sure their suppliers adhere to the pricing policy. However, I do not believe Nightforce has the same strict policy regarding their other products. When I was searching for the best NXS buy, I found everyone was within a dollar of each other on the scope, but anything else I wanted was available for negotiation: free shipping, discount on Nightforce software or ACI unit. They cannot discount their Nightforce scopes, but what they make on one can easily allow them to discount on other merchandise. You can't beat the system - so you learn to work around or within it. Good luck in your search.
Keep your eyes open here and on snipershide & 24hourcampfire. Used NXS scopes do come up for sale now and then, but they get snapped up pretty quick.