Just like Princess Diana before her, Kate Middleton’s fashion choices are setting off a style-frenzy. The $600+ Issa dress (left) she wore when she and Prince William announced their engagement on Tuesday sold out in 24 hours from British department store Harvey Nichols. And it’s not just Middleton's clothes that are in demand—sapphires are experiencing the biggest resurgence since, well, 1981, when Princess Diana first flashed the 18-carat sapphire ring. Jewelers report being "flooded" with requests. Hey, if you can’t be the fiancée of a prince, at least you can still dress like one!