Princess Di picked out her 18-carat oval sapphire engagment ring surrounded with diamonds in 1981. Her choice became legendary, because at the time, the ring cost $60,000, which meant that just about anyone with the money could purchase it. Haters called it "the commoner's sapphire" and turned up their noses at the fact that a royal would purchase something relatively plain. But the princess made the ring and rock iconic. Prince William slipped the same one on Kate Middleton's finger on the day of their engagement in 2010.