Very helpful, thank you.
So if a value is higher than cover price, you consider it incorrect?
Can you give me some of the ISBNs this is happening for?
For books that are currently in print? Of course, as one can buy it for this price (and almost certainly even less) at any bookstore. Out-of-print and rare titles obviously can have values MUCH higher than cover price. I’m not sure which online source(s) you scrape for the value data, but a current edition paperback (9781805501428) that sells for $11.99 should never have a value of $29.68, for example.
Cover Value Difference % Over
$20.00 $27.74 $7.74 38.70% 9781250340672
$16.99 $24.61 $7.62 44.85% 9781662527555
$17.99 $25.74 $7.75 43.08% 9781728239255
$11.99 $21.65 $9.66 80.57% 9781835259184
$10.99 $19.87 $8.88 80.80% 9781836186106
$11.99 $22.32 $10.33 86.16% 9781835254899
$19.99 $28.87 $8.88 44.42% 9780593625484
$28.00 $33.45 $5.45 19.46% 9781496749680
$18.99 $24.97 $5.98 31.49% 9781648756252
$19.99 $26.60 $6.61 33.07% 9781648756412
$16.99 $20.87 $3.88 22.84% 9781662519574
$12.99 $20.81 $7.82 60.20% 9780593691830
$16.99 $21.05 $4.06 23.90% 9781662519154
$19.99 $23.29 $3.30 16.51% 9781648755958
$9.99 $13.20 $3.21 32.13% 9781836185147
$27.99 $35.96 $7.97 28.47% 9781728270005
$28.00 $35.02 $7.02 25.07% 9781250351791
$30.00 $34.51 $4.51 15.03% 9780063223059
$30.00 $36.80 $6.80 22.67% 9781538742983
$18.99 $24.06 $5.07 26.70% 9780778334460
$16.99 $21.22 $4.23 24.90% 9781662521690
$16.99 $21.43 $4.44 26.13% 9781662510014
$16.99 $22.48 $5.49 32.31% 9781662526046
$11.99 $22.53 $10.54 87.91% 9781805501015
$10.99 $27.01 $16.02 145.77% 9781836187448
$10.99 $29.68 $18.69 170.06% 9781835252970
$11.99 $24.97 $12.98 108.26% 9781836185901
$12.99 $24.97 $11.98 92.22% 9781836183655
$11.99 $29.68 $17.69 147.54% 9781805501428
$28.00 $35.01 $7.01 25.04% 9781250369741
Looking at it like this, a few things jump out to me. CLZ appears to have especially large issues with trade paperbacks, specifically those published by Bookouture (a UK imprint) and Thomas & Mercer (an Amazon US imprint).
I checked some of these and they had weird high values indeed.
Strangely enough, when I updated the value through our sources, they all corrected to expected levels.
Will see if we can update all our values with our sources again.