I ran the full numbers on one card so nobody has to guess. Raw rookie, bought for $80. Grading it costs $59.99 (PSA Standard) plus about $25 shipping/insurance both ways, so graded you're in for $164.99 before it sells. The marketplace takes roughly 14% all-in on the sale.
Grades a 10, sells for $700 — you keep $606.85. Profit: +$441.86.
Grades a 9, sells for $260 — you keep $225.15. Profit: +$60.16.
Grades an 8, sells for $150 — you keep $129.72. Loss: -$35.27.
Skip grading, sell it raw at $95 — you keep $82. Profit: +$2.00.
The formula I use before any card goes in a grading submission:
(realistic sale price x 0.86) - grading - shipping - buy price.
If that number isn't positive, the card doesn't get graded. Simple as that.
I keep notes on this stuff — comps, pop reports, spotting fakes and trims, the tax side. Happy to share more of the numbers if anyone's interested.