The markup varies depending on the bottle and depending on whether we're talking retail or wholesale prices. But one rule of thumb -- and like all rules of thumb, there are about 1,000 variations -- says that restaurants should charge 2.5 x the wholesale price or 2 x the retail. Of course, some restaurants, those that gouge their diners more, charge higher prices. But generally speaking if a wholesaler charges $10 for a bottle, a retailer will ask about $15 for it and a restaurant will ask between $25 and $30.