Psyduck #SM199
PSA 10 sells for 42.7× a graded 9 ($1,002 vs $23.49).
PSA has given this card a ten 1.9× as often — 17.3% against 9.0%.
How CGC grades work
These are two different pools of submissions, so this compares what each grader did, not what either would do with the same card.