Porygon

Grading with PSA pays if your copy has better than a 15% chance of a 10.

6% of the 126 copies PSA has graded got a 10. People mostly send their cleanest copies, so a typical raw copy's odds are lower.

Raw (NM)

$4.76

TCGplayer

PSA 10

$380.00

6 sales

PSA 9

$44.85

15 sales

If it misses

$33.37

below 10, by PSA's grades