Sure nobody ever pays list price for this kind of watches, just as you never pay list price for a car.
Yes, I negotiated a good deal, but that doesn't mean I am going to wear this on a used strap. I am changing all my straps when I buy a used watch and then once a year. No way will I wear a watch on a strap which an unknown quantity of people have tried on.
If you look on eBay you will find many ex-display Lange and Patek straps being offered, most ADs will exchange them as a rule when the watch is sold, without the need for asking for it.