This is a comparison of 0.3ct ideal cut, E color, VVS1 clarity, round cut diamonds (click the dollar amount to be taken directly to the diamond):

James Allen: $820

Abazias: $993

Blue Nile: $1017

Brilliant Earth: $1110

White Flash: $1139

These diamonds are independently inspected and graded by GIA/AGS, which means you can trust their quality. The quality of these diamonds is identical--the only thing that is different is the price.