This is a comparison of 1ct ideal cut, D color, VVS2 clarity Oval cut diamonds (click the dollar amount to be taken directly to the diamond):

James Allen: $4840

Abazias: $5213

Blue Nile: $7010

Brilliant Earth: $7920

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.