The number 1 taking the top spot for most expensive engagement ring is the Chopard Blue Diamond ring with a whopping price tag of $1.5 billion. What's so special about this ring you may ask? Well, perhaps the pimped out blue diamond that makes any other diamond feel they've come up short and inadequate. The 18K white gold band is not too shabby either. Where can you find the natural source for this beastie of a ring? Welll, the blue diamond is usually found among boron deposits and that's where it gets its shade from.
Here's a picture of the beauty in all its glory:
