I have heard that I should not sell a diamond engagement ring for under 50-70 percent of the rappaport value. However, I don't know what a rappaport value is. The round, si1, .57 carat, F color diamond, 5.38x5.42x3.26 diamond (crysal, cloud), think to medium faceted girdle was bought from Blue Nile for $1990. We put a $400 platinum band on it. Why did a jeweler only offer $800? A company in New York offered "between $800-$1000". How reasonable is $1000? Is it reasonable to expect anything over $1000, such as $1200? Thanks All!