cost of half carat diamond
1 Quarter carat or less diamond, $125 to $500 set in 14 carat gold. 2  0.3 to half carat diamond, $750 to $1,000 set in 18 carat gold or platinum, possibly more if ASG/GIA certified.  For diamonds up to 0.75 carat, or smaller ASG/GIA certified stones, $1,000-$2,000.