Price differences for surveyed diamonds
Table 3. Average cost of all 17 stones based on their grading and the premium or discount[1] that their certificates attract.
| Stone # | GIA-GTL | AGSL | EGL USA | ||
| Price | Price | Diff. to GIA | Price | Diff. to GIA | |
| 1 | $2,576 | $2,296 | -11% | $2,458 | -5% |
| 2 | $2,922 | $2,922 | 0% | $2,758 | -6% |
| 3 | $4,248 | $4,426 | 4% | $3,634 | -14% |
| 4 | $4,540 | $4,541 | 0% | $3,925 | -14% |
| 5 | $1,522 | $1,456 | -4% | $1,527 | 0% |
| 6 | $1,496 | $1,964 | 31% | $1,478 | -1% |
| 7 | $2,075 | $1,915 | -8% | $1,707 | -18% |
| 8 | $1,607 | $1,501 | -7% | $1,569 | -2% |
| 9 | $2,058 | $2,219 | 8% | $1,696 | -18% |
| 10 | $2,453 | $2,212 | -10% | ||
| 11 | $2,952 | $2,668 | -10% | $2,624 | -11% |
| 12 | $2,653 | $2,398 | -10% | $2,103 | -21% |
| 13 | $2,152 | $2,152 | 0% | $2,137 | -1% |
| 14 | $4,127 | $5,907 | 43% | $4,716 | 14% |
| 15 | $8,451 | $7,264 | -14% | $6,739 | -20% |
| 16 | $8,255 | $7,708 | -7% | $6,323 | -23% |
| 17 | $2,246 | $2,047 | -9% | $1,892 | -16% |
| Average | $3,314 | $3,337 | 1% | $2,912 | -10% |
Figure 3. Price differences compared to similar GIA-GTL graded diamonds.
Each positive or negative difference on the chart corresponds to higher or
lower prices for similar diamonds listed for sale with respective reports.
Figure 4. 56% of the surveyed diamonds would cost less if sold with AGS
rather than GIA reports, mainly as a result of stricter clarity grading 80% of
the diamonds would cost less if bought with EGL rather than GIA reports.
Discounting of EGL graded diamonds was greater than any premiums as a result of
softer color grading.
[1] The premium/discount was calculated from a price study of more than 50,000 diamonds for sale online.