Online shoppers won’t find a price list or an “add to cart” button when they visit the website of iconic watchmaker Patek Philippe.  The most prominent visual on the home page is not a limited edition timepiece but a commercial featuring a father congratulating his young son for winning a cricket match. The ad ends with the slogan: “You never actually own a Patek Philippe. You merely look after it for the next generation.” Patek Philippe’s online store, where customers can look but not purchase, is certainly atypical of most shopping websites. But that’s kind of the point, Wharton marketing experts say. It’s also an excellent example of how some high-end retailers are dealing with a dilemma born of the digital age. How does a luxury brand retain its extravagant feel while catering to the growing horde of consumers who love to shop online? “Luxury is about scarcity, exclusivity.…