Um ... so my example of Rolex's markup wasn't a close enough analogue to MBW wholesale, so you use diamonds as an example?
Go to a wholesale shop, like a retail supplier for stationery or games/toys or anything that's not large, big ticket items and you'll see the range I'm talking about.
Hang on, why are we arguing over this again? You disagree that my initial statement of the markup the OP quoted was surprisingly low, especially seeing as the Rolex models they stock are sold at 50% of what dealers sell them for? Or do you just disagree that the retail business generally uses a 40%-60% off retail wholesale figure?