This is a comparison of 0.85ct ideal cut, F color, VS1 clarity round cut diamonds (click the dollar amount to be taken directly to the diamond):

James Allen: $4400

Blue Nile: $4938

Abazias: $5003

Brilliant Earth: $6560

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.