In jewellery making class you often hear how diamonds are used as accents rather than focal points. Yet any item increases 5 folds once this precious gem is added. Personally, I think both in cost and appearance. You get what you pay for and the devil is really in the details. Any jeweller passionate about his craft won't set a Burmese jade piece with cubic zircon. Yet I managed to find a jewellery store that sold the above ring, highly available mother-of-pearl with real diamonds, to beautiful effect.
Any diamond less than 0.3 carat in size is ungraded. So the difference is in the fire of the stone & the way it captures and redirects light, giving off a brilliance like no other. Ideally, it should have a disco ball effect across the room when the light falls on your diamonds. Any light, even when you are indoors. That is how refractive the precious stone is. When light enters at the perfect angle, it will create a mini supernova of a sparkle that should temporarily blind the observer.